TheseveralmammifersembeddedinthePampeanformation，whichmostlybelongtoextinctgenera，andsomeeventoextinctfamiliesororders，andwhichdiffernearly，ifnotquite，asmuchasdotheEocenemammifersofEuropefromlivingquadrupedshavingexistedcontemporaneouslywithmollusca，allstillinhabitingtheadjoiningsea，iscertainlyamoststrikingfact。Itis，however，farfrombeinganisolatedone;for，duringthelatetertiarydepositsofBritain，anelephant，rhinoceros，andhippopotamusco-existedwithmanyrecentlandandfresh-watershells;andinNorthAmerica，wehavethebestevidencethatamastodon，elephant，megatherium，megalonyx，mylodon，anextincthorseandox，likewiseco-

existedwithnumerousland，fresh-water，andmarinerecentshells。(Manyoriginalobservations，andasummaryonthissubject，aregiveninMr。

Lyell’spaperinthe“GeologicalProceedings“volume4page3andinhis“TravelsinNorthAmerica“volume1page164andvolume2page60。FortheEuropeananalogouscasesseeMr。Lyell’s“PrinciplesofGeology“6theditionvolume1page37。)TheenumerationoftheseextinctNorthAmericananimalsnaturallyleadsmetorefertotheformercloserrelationofthemammiferousinhabitantsofthetwoAmericas，whichIhavediscussedinmy“Journal，“andlikewisetothevastextentofcountryoverwhichsomeofthemranged：thusthesamespeciesoftheMegatherium，Megalonyx，Equus(asfarasthestateoftheirremainspermitsofidentification)，extendedfromtheSouthernUnitedStatesofNorthAmericatoBahiaBlanca，inlatitude39

degreesS。onthecoastofPatagonia。Thefactoftheseanimalshavinginhabitedtropicalandtemperateregions，doesnotappeartomeanygreatdifficulty，seeingthatattheCapeofGoodHopeseveralquadrupeds，suchastheelephantandhippopotamus，rangefromtheequatortolatitude35

degreessouth。ThecaseoftheMastodonAndiumisoneofmoredifficulty，foritisfoundfromlatitude36degreesS。over，asIhavereasontobelieve，nearlythewholeofBrazil，anduptheCordilleratoregionswhich，accordingtoM。d’Orbigny，borderonperpetualsnow，andwhicharealmostdestituteofvegetation：undoubtedlytheclimateoftheCordilleramusthavebeendifferentwhenthemastodoninhabitedit;butweshouldnotforgetthecaseoftheSiberianmammothandrhinoceros，asshowinghowsevereaclimatethelargerpachydermatacanendure;noroverlookthefactoftheguanacorangingatthepresentdayoverthehotlowdesertsofPeru，theloftypinnaclesoftheCordillera，andthedampforest-cladlandofSouthernTierradelFuego;thepuma，also，isfoundfromtheequatortotheStraitofMagellan，andIhaveseenitsfootstepsonlyalittlebelowthelimitsofperpetualsnowintheCordilleraofChile。

Attheperiod，sorecentinageologicalsense，whentheseextinctmammifersexisted，thetwoAmericasmusthaveswarmedwithquadrupeds，manyofthemofgiganticsize;for，besidesthosemoreparticularlyreferredtointhischapter，wemustincludeinthissameperiodthosewonderfullynumerousremains，somefewofthemspecifically，andothersgenericallyrelatedtothoseofthePampas，discoveredbyMM。LundandClauseninthecavesofBrazil。Finally，thefactsheregivenshowhowcautiousweoughttobeinjudgingoftheantiquityofaformationfromevenagreatamountofdifferencebetweentheextinctandlivingspeciesinanyoneclassofanimals;——weoughteventobecautiousinacceptingthegeneralproposition，thatchangeinorganicformsandlapseoftimeareatall，necessarily，correlatives……

LOCALITIESWITHINTHEREGIONOFTHEPAMPASWHEREGREATBONESHAVEBEEN

FOUND。

Thefollowinglist，whichincludeseveryaccountwhichIhavehithertometwithofthediscoveryoffossilmammiferousremainsinthePampas，maybehereafterusefultoageologistinvestigatingthisregion，andittendstoshowtheirextraordinaryabundance。Iheardofandsawmanyfossils，theoriginalpositionofwhichIcouldnotascertain;andIreceivedmanystatementstoovaguetobehereinserted。Beginningtothesouth：——wehavethetwostationsinBahiaBlanca，describedinthischapter，whereatP。

Alta，theMegatherium，Megalonyx，Scelidotherium，Mylodon，Holophractus(oranalliedgenus)，Toxodon，Macrauchenia，andanEquuswerecollected;andatM。HermosoaCtenomys，Hydrochaerus，someotherrodentsandthebonesofagreatmegatheroidquadruped。Closenorth-eastoftheS。Tapalguen，wehavetheRios’Huesos’(i。e。“bones“)，whichprobablytakesitsnamefromlargefossilbones。NearVillaNuevo，andatLasAverias，notfarfromtheSalado，threenearlyperfectskeletons，oneoftheMegatherium，oneoftheGlyptodonclavipes，andoneofsomegreatDasypoidquadruped，werefoundbytheagentofSirW。Parish(seehiswork“BuenosAyres“etc。page171)。I

haveseenthetoothofaMastodonfromtheSalado;alittlenorthwardofthisriver，onthebordersofalakeneartheG。delMonte，Isawmanybones，andonelargepieceofdermalarmour;higheruptheSalado，thereisaplacecalledMonte“Huesos。”OntheMatanzas，abouttwentymilessouthofBuenosAyres，theskeleton(videpage178of“BuenosAyres“etc。bySirW。

Parish)ofaGlyptodonwasfoundaboutfivefeetbeneaththesurface;herealso(seeCatalogueofRoyalCollegeofSurgeons)remainsofGlyptodonclavipes，G。ornatus，andG。reticulatuswerefound。SignorAngelis，inaletterwhichIhaveseen，referstosomegreatremainsfoundinBuenosAyres，atadepthoftwentyvarasfromthesurface。SevenleaguesnorthofthiscitythesameauthorfoundtheskeletonsofMylodonrobustusandGlyptodonornatus。FromthisneighbourhoodhehaslatelysenttotheBritishMuseumthefollowingfossils：——RemainsofthreeorfourindividualsofMegatherium;ofthreespeciesofGlyptodon;ofthreeindividualsoftheMastodonAndium;ofMacrauchenia;ofasecondspeciesofToxodon，differentfromT。Platensis;andlastly，oftheMachairodus，awonderfullargecarnivorousanimal。M。d’OrbignyhaslatelyreceivedfromtheRecolate“Voyage“Pal。page144)，nearBuenosAyres，atoothofToxodonPlatensis。

Proceedingnorthward，alongthewestbankoftheParana，wecometotheRioLuxan，wheretwoskeletonsoftheMegatheriumhavebeenfound;andlately，withineightleaguesofthetownofLuxan，Dr。F。X。Munizhascollected(“BritishPacket“BuenosAyresSeptember25，1841)，fromanaveragedepthofeighteenfeet，verynumerousremains，ofnolessthan，ashebelieves，ninedistinctspeciesofmammifers。AtAreco，largeboneshavebeenfound，whicharebelieved，bytheinhabitants，tohavebeenchangedfromsmallbones，bythewateroftheriver！AtArrecifes，theGlyptodon，senttotheCollegeofSurgeons，wasfound;andIhaveseentwoteethofaMastodonfromthisquarter。AtS。Nicolas，M。d’OrbignyfoundremainsofaCanis，Ctenomys，andKerodon;andM。Isabelle(“Voyage“page332)referstoagiganticArmadillofoundthere。AtS。Carlos，Iheardofgreatbones。A

littlebelowthemouthoftheCarcarana，thetwoskeletonsofMastodonwerefound;onthebanksofthisriver，nearS。Miguel，IfoundteethoftheMastodonandToxodon;and“Falkner“(page55)describestheosseousarmourofsomegreatanimal;Iheardofmanyotherbonesinthisneighbourhood。I

haveseen，Imayadd，inthepossessionofMr。Caldcleugh，thetoothofaMastodonAndium，saidtohavebeenfoundinParaguay;Imayherealsorefertoastatementinthisgentleman’stravels(volume1page48)，ofagreatskeletonhavingbeenfoundintheprovinceofBoliviainBrazil，ontheR。

delasContas。ThefurthestpointwestwardinthePampas，atwhichIhaveHEARDoffossilbones，washighuponthebanksofR。Quinto。

InEntreRios，besidestheremainsoftheMastodon，Toxodon，Equus，andagreatDasypoidquadrupednearSt。FeBajada，IreceivedanaccountofboneshavingbeenfoundalittleS。E。ofP。Gorda(ontheParana)，andofanentireskeletonatMatanzas，ontheArroyodelAnimal。

InBandaOriental，besidestheremainsoftheToxodon，Mylodon，andtwoskeletonsofgreatanimalswithosseousarmour(distinctfromthatoftheGlyptodon)，foundontheArroyosSarandisandBerquelo，M。Isabelle(“Voyage“page322)says，manyboneshavebeenfoundneartheR。Negro，andontheR。Arapey，anaffluentoftheParaguay，inlatitude30degrees40

minutessouth。IheardofbonesnearthesourceoftheA。Vivoras。IsawtheremainsofaDasypoidquadrupedfromtheArroyoSeco，closetoM。

Video;andM。d’Orbignyrefers(“Voyage“Geolog。page24)，toanotherfoundonthePedernal，anaffluentoftheSt。Lucia;andSignorAngelis，inaletter，statesthatathirdskeletonofthisfamilyhasbeenfound，nearCanelones。IsawatoothoftheMastodonfromTalas，anotheraffluentoftheSt。Lucia。ThemosteasternpointatwhichIheardofgreatboneshavingbeenfound，wasatSolisGrande，betweenM。VideoandMaldonado。

CHAPTERV。ONTHEOLDERTERTIARYFORMATIONSOFPATAGONIAANDCHILE。

RioNegro。

S。Josef。

PortDesire，whitepumiceousmudstonewithInfusoria。

PortS。Julian。

SantaCruz，basalticlavaof。

P。Gallegos。

EasternTierradelFuego;leavesofextinctbeech-trees。

SummaryonthePatagoniantertiaryformations。

TertiaryformationsoftheWesternCoast。

ChonosandChiloegroups，volcanicrocksof。

Concepcion。

Navidad。

Coquimbo。

Summary。

Ageofthetertiaryformations。

Linesofelevation。

Silicifiedwood。

ComparativerangesoftheextinctandlivingmolluscaontheWestCoastofS。America。

Climateofthetertiaryperiod。

OnthecausesoftheabsenceofrecentconchiferousdepositsonthecoastofS。America。

Onthecontemporaneousdepositionandpreservationofsedimentaryformations。

RIONEGRO。

IcanaddlittletothedetailsgivenbyM。d’Orbignyonthesandstoneformationofthisdistrict。(“Voyage“PartGeolog。pages57-65。)Thecliffstothesouthoftheriverareabouttwohundredfeetinheight，andarecomposedofsandstoneofvarioustintsanddegreesofhardness。Onelayer，whichthinnedoutatbothends，consistedofearthymatter，ofapalereddishcolour，withsomegypsum，andverylike(Ispeakaftercomparisonofthespecimensbroughthome)Pampeanmud：abovethiswasalayerofcompactmarlyrockwithdendriticmanganese。Manyblocksofaconglomerateofpumice-pebblesembeddedinhardsandstonewerestrewedatthefootofthecliff，andhadevidentlyfallenfromabove。AfewmilesN。E。ofthetown，Ifound，lowdowninthesandstone，abed，afewinchesinthickness，ofawhite，friable，harsh-feelingsediment，whichadherestothetongue，isofeasyfusibility，andoflittlespecificgravity;examinedunderthemicroscope，itisseentobepumiceoustuff，formedofbrokentransparentcrystals。Inthecliffssouthoftheriver，thereis，also，athinlayerofnearlysimilarnature，butfinergrained，andnotsowhite;itmighteasilyhavebeenmistakenforacalcareoustuff，butitcontainsnolime：thissubstancepreciselyresemblesamostwidelyextendedandthickformationinSouthernPatagonia，hereaftertobedescribed，andwhichisremarkableforbeingpartiallyformedofinfusoria。Thesebeds，conjointlywiththeconglomerateofpumice，areinteresting，asshowingthenatureofthevolcanicactionintheCordilleraduringthisoldtertiaryperiod。

Inabedatthebaseofthesoutherncliffs，M。d’Orbignyfoundtwoextinctfresh-watershells，namely，aUnioandChilina。Thisbedrestedononewithbonesofanextinctrodent，namely，theMegamysPatagoniensis;andthisagainonanotherwithextinctmarineshells。ThespeciesfoundbyM。

d’Orbignyindifferentpartsofthisformationconsistof：——

1。OstreaPatagonica，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe，andwholecoastofPatagonia)。

2。OstreaFerrarisi，d’Orbigny，“Voyage，Pal。”

3。OstreaAlvarezii，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe，andS。

Josef)。

4。PectenPatagoniensis，d’Orbigny，“Voyage，Pal。”

5。VenusMunsterii，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe)。

6。ArcaBonplandiana，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe)。

AccordingtoM。d’Orbigny，thesandstoneextendswestwardalongthecoastasfarasPortS。Antonio，anduptheR。Negrofarintotheinterior：

northwardItracedittothesouthernsideoftheRioColorado，whereitformsalowdenudedplain。Thisformation，thoughcontemporaneouswiththatoftherestofPatagonia，isquitedifferentinmineralogicalcomposition，beingconnectedwithitonlybytheonethinwhitelayer：thisdifferencemaybereasonablyattributedtothesedimentbroughtdowninancienttimesbytheRioNegro;bywhichagency，also，wecanunderstandthepresenceofthefresh-watershells，andofthebonesoflandanimals。Judgingfromtheidentityoffouroftheaboveshells，thisformationiscontemporaneous(asremarkedbyM。d’Orbigny)withthatunderthePampeandepositinEntreRiosandinBandaOriental。Thegravelcappingthesandstoneplain，withitscalcareouscementandnodulesofgypsum，isprobably，fromthereasonsgivenintheFirstChapter，contemporaneouswiththeuppermostbedsofthePampeanformationontheupperplainnorthoftheColorado。

SANJOSEF。

Myexaminationherewasveryshort：thecliffsareaboutahundredfeethigh;thelowerthirdconsistsofyellowish-brown，soft，slightlycalcareous，muddysandstone，partsofwhichwhenstruckemitafetidsmell。

InthisbedthegreatOstraeaPatagonica，oftenmarkedwithdendriticmanganeseandsmallcoral-lines，wereextraordinarilynumerous。Ifoundherethefollowingshells：——

1。OstreaPatagonica，d’Orbigny，“Voyage，Pal。”(alsoatSt。FeandwholecoastofPatagonia)。

2。OstreaAlvarezii，d’Orbigny，“Voyage，Pal。”(alsoatSt。FeandR。

Negro)。

3。PectenParanensis，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe，S。Julian，andPortDesire)。

4。PectenDarwinianus，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe)。

5。Pectenactinodes，G。B。Sowerby。

6。TerebratulaPatagonica，G。B。Sowerby(alsoS。Julian)。

7。CastsofaTurritella。

ThefourfirstofthesespeciesoccuratSt。FeinEntreRios，andthetwofirstinthesandstoneoftheRioNegro。Abovethisfossiliferousmass，thereisastratumofveryfine-grained，palebrownmudstone，includingnumerouslaminaeofselenite。Allthestrataappearhorizontal，butwhenfollowedbytheeyeforalongdistance，theyareseentohaveasmalleasterlydip。Onthesurfacewehavetheporphyriticgravel，andonitsandwithrecentshells。

NUEVOGULF。

>FromspecimensandnotesgivenmebyLieutenantStokes，itappearsthatthelowerbedconsistsofsoftmuddysandstone，likethatofS。Josef，withmanyimperfectshells，includingthePectenParanensis，d’Orbigny，castsofaTurritellaandScutella。Onthistherearetwostrataofthepalebrownmudstone，alsolikethatofS。Josef，separatedbyadarker-coloured，moreargillaceousvariety，includingtheOstreaPatagonica。ProfessorEhrenberghasexaminedthismudstoneforme：hefindsinitthreealreadyknownmicroscopicorganisms，envelopedinafine-grainedpumiceoustuff，whichI

shallhaveimmediatelytodescribeindetail。Specimensbroughttomefromtheuppermostbed，northoftheRioChupat，consistofthissamesubstance，butofawhitercolour。

Tertiarystrata，suchasheredescribed，appeartoextendalongthewholecoastbetweenRioChupatandPortDesire，exceptwhereinterruptedbytheunderlyingclaystoneporphyry，andbysomemetamorphicrocks;thesehardrocks，Imayadd，arefoundatintervalsoveraspaceofaboutfivedegreesoflatitude，fromPointUniontoapointbetweenPortS。JulianandS。

Cruz，andwillbedescribedintheensuingchapter。ManygiganticspecimensoftheOstraeaPatagonicawerecollectedintheGulfofSt。George。

PORTDESIRE。

Agoodsectionofthelowestfossiliferousmass，aboutfortyfeetinthickness，restingonclaystoneporphyry，isexhibitedafewmilessouthoftheharbour。Theshellssufficientlyperfecttoberecognisedconsistof：——

1。OstreaPatagonica，d’Orbigny，(alsoatSt。Fe，andwholecoastofPatagonia)。

2。PectenParanensis，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe，S。Josef，S。Julian)。

3。Pectencentralis，G。B。Sowerby(alsoatS。JulianandS。Cruz)。

4。Cucullaeaalta，G。B。Sowerby(alsoatS。Cruz)。

5。Nuculaornata，G。B。Sowerby。

6。TurritellaPatagonica，G。B。Sowerby。

Thefossiliferousstrata，whennotdenuded，areconformablycoveredbyaconsiderablethicknessofthefine-grainedpumiceousmudstone，dividedintotwomasses：thelowerhalfisveryfine-grained，slightlyunctuous，andsocompactastobreakwithasemi-conchoidalfracture，thoughyieldingtothenail;itincludeslaminaeofselenite：theupperhalfpreciselyresemblestheonelayerattheRioNegro，andwiththeexceptionofbeingwhiter，theupperbedsatSanJosefandNuevoGulf。Inneithermassisthereanytracetothenakedeyeoforganicforms。Takingtheentiredeposit，itisgenerallyquitewhite，oryellowish，orfeeblytintedwithgreen;itiseitheralmostfriableunderthefinger，orashardaschalk;itisofeasyfusibility，oflittlespecificgravity，isnotharshtothetouch，adherestothetongue，andwhenbreathedonexhalesastrongaluminousodour;itsometimescontainsaverylittlecalcareousmatter，andtraces(besidestheincludedlaminae)ofgypsum。Underthemicroscope，accordingtoProfessorEhrenberg，itconsistsofminute，triturated，cellular，glassyfragmentsofpumice，withsomebrokencrystals。(“Monatsberichtendekonig。Akad。zuBerlin“vomApril1845。)Intheminuteglassyfragments，ProfessorEhrenbergrecognisesorganicstructures，whichhavebeenaffectedbyvolcanicheat：inthespecimensfromthisplace，andfromPortS。Julian，hefindssixteenPolygastricaandtwelvePhytolitharia。Oftheseorganisms，sevenarenewforms，theothersbeingpreviouslyknown：allareofmarine，andchieflyofoceanic，origin。Thisdeposittothenakedeyeresemblesthecrustwhichoftenappearsonweatheredsurfacesoffeldspathicrocks;itlikewiseresemblesthosebedsofearthyfeldspathicmatter，sometimesinterstratifiedwithporphyriticrocks，asisthecaseinthisverydistrictwiththeunderlyingpurpleclaystoneporphyry。Fromexaminingspecimensunderacommonmicroscope，andcomparingthemwithotherspecimensundoubtedlyofvolcanicorigin，IhadcometothesameconclusionwithProfessorEhrenberg，namely，thatthisgreatdeposit，initsfirstorigin，isofvolcanicnature。

PORTS。JULIAN。

(FIGURE17。SECTIONOFTHESTRATAEXHIBITEDINTHECLIFFSOFTHENINETY

FEETPLAINATPORTS。JULIAN。

(Sectionthroughbedsfromtoptobottom：A，B，C，D，E，F。))

Onthesouthsideoftheharbour，Figure17givesthenatureofthebedsseeninthecliffsoftheninetyfeetplain。Beginningatthetop：——

1st，theearthymass(AA)，includingtheremainsoftheMacrauchenia，withrecentshellsonthesurface。

Second，theporphyriticshingle(B)，whichinitslowerpartisinterstratified(owing，Ibelieve，toredispositionduringdenudation)withthewhitepumiceousmudstone。

Third，thiswhitemudstone，abouttwentyfeetinthickness，anddividedintotwovarieties(CandD)，bothcloselyresemblingthelower，fine-

grained，moreunctuousandcompactkindatPortDesire;and，asatthatplace，includingmuchselenite。

Fourth，afossiliferousmass，dividedintothreemainbeds，ofwhichtheuppermostisthin，andconsistsofferruginoussandstone，withmanyshellsofthegreatoysterandPectenParanensis;themiddlebed(E)isayellowishearthysandstoneaboundingwithScutellae;andthelowestbed(F)

isanindurated，greenish，sandyclay，includinglargeconcretionsofcalcareoussandstone，manyshellsofthegreatoyster，andinpartsalmostmadeupoffragmentsofBalanidae。Outofthesethreebeds，Iprocuredthefollowingtwelvespecies，ofwhichthetwofirstwereexceedinglynumerousinindividuals，asweretheTerebratulaeandTurritellaeincertainlayers：——

1。OstreaPatagonica，d’Orbigny，“Voyage，Pal。”(alsoatSt。Fe，andwholecoastofPatagonia)。

2。PectenParanensis，d’Orbigny，“Voyage，Pal。”(St。Fe，S。Josef，PortDesire)。

3。Pectencentralis，G。B。Sowerby(alsoatPortDesireandS。Cruz)。

4。Pectengeminatus，G。B。Sowerby。

5。TerebratulaPatagonica，G。B。Sowerby(alsoS。Josef)。

6。Struthiolariaornata，G。B。Sowerby(alsoS。Cruz)。

7。FususPatagonicus，G。B。Sowerby。

8。FususNoachinus，G。B。Sowerby。

9。Scalariarugulosa，G。B。Sowerby。

10。Turritellaambulacrum，G。B。Sowerby(alsoS。Cruz)。

11。Pyrula，castof，likeP。ventricosaofSowerby，TankCat。

12。Balanusvarians，G。B。Sowerby。

13。Scutella，differingfromthespeciesfromNuevoGulf。

AttheheadoftheinnerharbourofPortS。Julian，thefossiliferousmassisnotdisplayed，andthesea-cliffsfromthewater’sedgetoaheightofbetweenoneandtwohundredfeetareformedofthewhitepumiceousmudstone，whichhereincludesinnumerable，far-extended，sometimeshorizontal，sometimesinclinedorverticallaminaeoftransparentgypsum，oftenaboutaninchinthickness。Furtherinland，withtheexceptionofthesuperficialgravel，thewholethicknessofthetruncatedhills，whichrepresentaformerlycontinuousplain950feetinheight，appearstobeformedofthiswhitemudstone：hereandthere，however，atvariousheights，thinearthylayers，containingthegreatoyster，PectenParanensisandTurritellaambulacrum，areinterstratified;thusshowingthatthewholemassbelongstothesameepoch。Inowherefoundevenafragmentofashellactuallyinthewhitedeposit，andonlyasinglecastofaTurritella。OutoftheeighteenmicroscopicorganismsdiscoveredbyEhrenberginthespecimensfromthisplace，tenarecommontothesamedepositatPortDesire。Imayaddthatspecimensofthiswhitemudstone，withthesameidenticalcharacterswerebroughtmefromtwopoints，——onetwentymilesnorthofS。Julian，whereawidegravel-cappedplain，350feetinheight，isthuscomposed;andtheotherfortymilessouthofS。Julian，where，ontheoldcharts，thecliffsaremarkedas“ChalkHills。”

SANTACRUZ。

Thegravel-cappedcliffsatthemouthoftheriverare355feetinheight：

thelowerpart，toathicknessoffiftyorsixtyfeet，consistsofamoreorlesshardened，darkish，muddy，orargillaceoussandstone(likethelowestbedofPortDesire)，containingverymanyshells，somesilicifiedandsomeconvertedintoyellowcalcareousspar。Thegreatoysterisherenumerousinlayers;theTrigonoceliaandTurritellaarealsoverynumerous：

itisremarkablethatthePectenParanensis，socommoninallotherpartsofthecoast，ishereabsent：theshellsconsistof：——

1。OstreaPatagonica，d’Orbigny;“VoyagePal。”(alsoatSt。FeandwholecoastofPatagonia)。

2。Pectencentralis，G。B。Sowerby(alsoP。DesireandS。Julian)。

3。VenusmeridionalisofG。B。Sowerby。

4。CrassatellaLyellii，G。B。Sowerby。

5。Cardiumpuelchum，G。B。Sowerby。

6。CarditaPatagonica，G。B。Sowerby。

7。Mactrarugata，G。B。Sowerby。

8。MactraDarwinii，G。B。Sowerby。

9。Cucullaeaalta，G。B。Sowerby(alsoP。Desire)。

10。Trigonoceliainsolita，G。B。Sowerby。

11。Nucula(？)glabra，G。B。Sowerby。

12。Crepidulagregaria，G。B。Sowerby。

13。Volutaalta，G。B。Sowerby。

14。Trochuscollaris，G。B。Sowerby。

15。Naticasolida(？)，G。B。Sowerby16。Struthiolariaornata，G。B。Sowerby(alsoP。Desire)。

17。Turritellaambulacrum，G。B。Sowerby(alsoP。S。Julian)。

ImperfectfragmentsofthegeneraByssoarca，Artemis，andFusus。

Theupperpartofthecliffisgenerallydividedintothreegreatstrata，differingslightlyincomposition，butessentiallyresemblingthepumiceousmudstoneoftheplacesfarthernorth;thedeposit，however，hereismorearenaceous，ofgreaterspecificgravity，andnotsowhite：itisinterlacedwithnumerousthinveins，partiallyorquitefilledwithtransversefibresofgypsum;thesefibresweretooshorttoreachacrossthevein，havetheirextremitiescurvedorbent：inthesameveinswiththegypsum，andlikewiseinseparateveinsaswellasinlittlenests，thereismuchpowderysulphateofmagnesia(asascertainedbyMr。Reeks)inanuncompressedform：

Ibelievethatthissalthasnotheretoforebeenfoundinveins。Ofthethreebeds，thecentraloneisthemostcompact，andmorelikeordinarysandstone：itincludesnumerousflattenedsphericalconcretions，oftenunitedlikeanecklace，composedofhardcalcareoussandstone，containingafewshells：someoftheseconcretionswerefourfeetindiameter，andinahorizontallineninefeetapart，showingthatthecalcareousmattermusthavebeendrawntothecentresofattraction，fromadistanceoffourfeetandahalfonbothsides。Intheupperandlowerfiner-grainedstrata，therewereotherconcretionsofagreycolour，containingcalcareousmatter，andsofine-grainedandcompact，asalmosttoresembleporcelain-

rock：IhaveseenexactlysimilarconcretionsinavolcanictufaceousbedinChiloe。Althoughinthisupperfine-grainedstrata，organicremainswereveryrare，yetInoticedafewofthegreatoyster;andinoneincludedsoftferruginouslayer，thereweresomespecimensoftheCucullaeaalta(foundatPortDesireinthelowerfossiliferousmass)andoftheMactrarugata，whichlattershellhasbeenpartiallyconvertedintogypsum。

(FIGURE18。SECTIONOFTHEPLAINSOFPATAGONIA，ONTHEBANKSOFTHES。

CRUZ。

(Sectionthroughstrata(fromtoptobottom))：

Surfaceofplainwitherraticboulders;1，146feetabovethesea。

a。Gravelandboulders，212feetthick。

b。Basalticlava，322feetthick。

c，dande。Sedimentarylayers，bedofsmallpebblesandtalusrespectively，total592feetthick。

RiverofS。Cruz;here280feetabovesea。)

InascendingthevalleyoftheS。Cruz，theupperstrataofthecoast-

cliffsareprolonged，withnearlythesamecharacters，forfiftymiles：ataboutthispoint，theybegininthemostgradualandscarcelyperceptiblemanner，tobebandedwithwhitelines;andafterascendingtenmilesfarther，wemeetwithdistinctthinlayersofwhitish，greenish，andyellowishfine-grained，fusiblesediments。Ateightymilesfromthecoast，inacliffthuscomposed，therewereafewlayersofferruginoussandstone，andofanargillaceoussandstonewithconcretionsofmarllikethoseinthePampas。(Atthisspot，foraspaceofthree-quartersofamilealongthenorthsideoftheriver，andforawidthofhalfamile，therehasbeenagreatslip，whichhasformedhillsbetweensixtyandseventyfeetinheight，andhastiltedthestrataintohighlyinclinedandevenverticalpositions。Thestratagenerallydippedatanangleof45degreestowardstheclifffromwhichtheyhadslided。Ihaveobservedinslips，bothonasmallandlargescale，thatthisinwarddipisverygeneral。Isitduetothehydrostaticpressureofwaterpercolatingwithdifficultythroughthestrataactingwithgreaterforceatthebaseofthemassthanagainsttheupperpart？)Atonehundredmilesfromthecoast，thatisatacentralpointbetweentheAtlanticandtheCordillera，wehavethesectioninFigure18。

Theupperhalfofthesedimentarymass，underthebasalticlava，consistsofinnumerablezonesofperfectlywhitebrightgreen，yellowishandbrownish，fine-grained，sometimesincoherent，sedimentarymatter。Thewhite，pumiceous，trachytictuff-likevarietiesareofrathergreaterspecificgravitythanthepumiceousmudstoneonthecoasttothenorth;

someofthelayers，especiallythebrownerones，arecoarser，sothatthebrokencrystalsaredistinguishablewithaweaklens。Thelayersvaryincharacterinshortdistances。WiththeexceptionofafewoftheOstreaPatagonica，whichappearedtohaverolleddownfromthecliffabove，noorganicremainswerefound。Thechiefdifferencebetweentheselayerstakenasawhole，andtheupperbedsbothatthemouthoftheriverandonthecoastnorthward，seemstolieintheoccasionalpresenceofmorecolouringmatter，andinthesupplyhavingbeenintermittent;thesecharacters，aswehaveseen，verygraduallydisappearindescendingthevalley，andthisfactmayperhapsbeaccountedforbythecurrentsofamoreopenseahavingblendedtogetherthesedimentfromadistantandintermittentsource。

Thecolouredlayersintheforegoingsectionrestonamass，apparentlyofgreatthickness(butmuchhiddenbythetalus)，ofsoftsandstone，almostcomposedofminutepebbles，fromone-tenthtotwo-tenthsofaninchindiameter，oftherocks(withtheentireexceptionofthebasalticlava)

composingthegreatbouldersonthesurfaceoftheplain，andprobablycomposingtheneighbouringCordillera。Fivemileshigherupthevalley，andagainthirtymileshigherup(thatistwentymilesfromthenearestrangeoftheCordillera)，thelowerplainincludedwithintheupperescarpments，isformed，asseenonthebanksoftheriver，ofanearlysimilarbutfiner-grained，moreearthy，laminatedsandstone，alternatingwithargillaceousbeds，andcontainingnumerousmoderatelysizedpebblesofthesamerocks，andsomeshellsofthegreatOstreaPatagonica。(Ifoundatbothplaces，butnotinsitu，quantitiesofconiferousandordinarydicotyledonoussilicifiedwood，whichwasexaminedformebyMr。R。Brown。)

Asmostoftheseshellshadbeenrolledbeforebeinghereembedded，theirpresencedoesnotprovethatthesandstonebelongstothegreatPatagoniantertiaryformation，fortheymighthavebeenredepositedinit，whenthevalleyexistedasasea-strait;butasamongstthepebblestherewerenoneofbasalt，althoughthecliffsonbothsidesofthevalleyarecomposedofthisrock，Ibelievethatthesandstonedoesbelongtothisformation。Atthehighestpointtowhichweascended，twentymilesdistantfromthenearestslopeoftheCordillera，Icouldseethehorizontallyzonedwhitebeds，stretchingundertheblackbasalticlava，closeuptothemountains;

sothatthevalleyoftheS。CruzgivesafairideaoftheconstitutionofthewholewidthofPatagonia。

BASALTICLAVAOFTHES。CRUZ。

Thisformationisfirstmetwithsixty-sevenmilesfromthemouthoftheriver;thenceitextendsuninterruptedly，generallybutnotexclusivelyonthenorthernsideofthevalley，closeuptotheCordillera。Thebasaltisgenerallyblackandfine-grained，butsometimesgreyandlaminated;itcontainssomeolivine，andhighupthevalleymuchglassyfeldspar，where，also，itisoftenamygdaloidal;itisneverhighlyvesicular，exceptonthesidesofrentsandontheupperandlower，sphericallylaminatedsurfaces。

Itisoftencolumnar;andinoneplaceIsawmagnificentcolumns，eachfacetwelvefeetinwidth，withtheirintersticesfilledupwithcalcareoustuff。Thestreamsrestconformablyonthewhitesedimentarybeds，butI

nowheresawtheactualjunction;nordidIanywhereseethewhitebedsactuallysuperimposedonthelava;butsomewayupthevalleyatthefootoftheuppermostescarpments，theymustbethussuperimposed。Moreover，atthelowestpointdownthevalley，wherethestreamsthinoutandterminateinirregularprojections，thespacesorintervalsbetweentheseprojectionsarefilleduptothelevelofthenowdenudedandgravel-cappedsurfacesoftheplains，withthewhite-zonedsedimentarybeds;provingthatthismattercontinuedtobedepositedafterthestreamshadflowed。Hencewemayconcludethatthebasaltiscontemporaneouswiththeupperpartsofthegreattertiaryformation。

Thelavawherefirstmetwithis130feetinthickness：itthereconsistsoftwo，three，orperhapsmorestreams，dividedfromeachotherbyvesicularspheroidslikethoseonthesurface。Fromthestreamshaving，asitappears，extendedtodifferentdistances，theterminalpointsareofunequalheights。Generallythesurfaceofthebasaltissmooththeminoneparthighupthevalley，itwassounevenandhummocky，thatuntilI

afterwardssawthestreamsextendingcontinuouslyonbothsidesofthevalleyuptoaheightofaboutthreethousandfeetclosetotheCordillera，Ithoughtthatthecratersoferuptionwereprobablycloseathand。ThishummockysurfaceIbelievetohavebeencausedbythecrossingandheapingupofdifferentstreams。Inoneplace，therewereseveralroundedridgesabouttwentyfeetinheight，someofthemasbroadashigh，andsomebroader，whichcertainlyhadbeenformedwhilstthelavawasfluid，forintransversesectionseachridgewasseentobeconcentricallylaminated，andtobecomposedofimperfectcolumnsradiatingfromcommoncentres，likethespokesofwheels。

Thebasalticmasswherefirstmetwithis，asIhavesaid，130feetinthickness，and，thirty-fivemileshigherupthevalley，itincreasesto322

feet。Inthefirstfourteenandahalfmilesofthisdistance，theuppersurfaceofthelava，judgingfromthreemeasurementstakenabovetheleveloftheriver(ofwhichtheapparentlyveryuniforminclinationhasbeencalculatedfromitstotalheightatapoint135milesfromthemouth)，slopestowardstheAtlanticatanangleofonly0degrees7minutestwentyseconds：thismustbeconsideredonlyasanapproximatemeasurement，butitcannotbefarwrong。Takingthewholethirty-fivemiles，theuppersurfaceslopesatanangleof0degrees10minutes53seconds;butthisresultisofnovalueinshowingtheinclinationofanyonestream，forhalfwaybetweenthetwopointsofmeasurement，thesurfacesuddenlyrisesbetweenonehundredandtwohundredfeet，apparentlycausedbysomeoftheuppermoststreamshavingextendedthusfarandnofarther。Fromthemeasurementmadeatthesetwopoints，thirty-fivemilesapart，themeaninclinationofthesedimentarybeds，overwhichthelavahasflowed，isNOW

(afterelevationfromunderthesea)only0degrees7minutes52seconds：

forthesakeofcomparison，itmaybementionedthatthebottomofthepresentseainalinefromthemouthoftheS。CruztotheFalklandIslands，fromadepthofseventeenfathomstoadepthofeighty-fivefathoms，declinesatanangleof0degrees1minute22seconds;betweenthebeachandthedepthofseventeenfathoms，theslopeisgreater。Fromapointabouthalf-wayupthevalley，thebasalticmassrisesmoreabruptlytowardsthefootoftheCordillera，namely，fromaheightof1，204feet，toabout3，000feetabovethesea。

Thisgreatdelugeoflavaisworthy，initsdimensions，ofthegreatcontinenttowhichitbelongs。TheaggregatestreamshaveflowedfromtheCordilleratoadistance(unparalleled，Ibelieve，inanycaseyetknown)

ofaboutonehundredgeographicalmiles。Neartheirfurthestextremitytheirtotalthicknessis130feet，whichincreasethirty-fivemilesfartherinland，aswehavejustseen，to322feet。TheleastinclinationgivenbyM。E。deBeaumontoftheuppersurfaceofalava-stream，namely0degrees30minutes，isthatofthegreatsubaerialeruptionin1783fromSkaptarJukulinIceland;andM。E。deBeaumontshowsthatitmusthavefloweddownameaninclinationoflessthan0degrees20minutes。(“Memoirespourservir“etc。pages178and217。)Butwenowseethatunderthepressureofthesea，successivestreamshaveflowedoverasmoothbottomwithameaninclinationofnotmorethan0degrees7minutes52seconds;andthattheuppersurfaceoftheterminalportion(overaspaceoffourteenandahalfmiles)hasaninclinationofnotmorethan0degrees7minutes20seconds。

IftheelevationofPatagoniahasbeengreaternearertheCordillerathanneartheAtlantic(asisprobable)，thentheseanglesarenowalltoolarge。Imustrepeat，thatalthoughtheforegoingmeasurements，whichwereallcarefullytakenwiththebarometer，maynotbeabsolutelycorrect，theycannotbewidelyerroneous。

SouthwardoftheS。Cruz，thecliffsofthe840feetplainextendtoCoyInlet，andowingtothenakedpatchesofthewhitesediment，theyaresaidonthechartstobe“likethecoastofKent。”AtCoyInletthehighplaintrendsinland，leavingflat-toppedoutliers。AtPortGallegos(latitude51

degrees35minutes，andninetymilessouthofS。Cruz)，IaminformedbyCaptainSulivan，R。N。thatthereisagravel-cappedplainfromtwotothreehundredfeetinheight，formedofnumerousstrata，somefine-grainedandpale-coloured，liketheupperbedsatthemouthoftheS。Cruz，othersratherdarkandcoarser，soastoresemblegritstonesortuffs;theselatterincluderatherlargefragmentsofapparentlydecomposedvolcanicrocks;thereare，also，includedlayersofgravel。Thisformationishighlyremarkable，fromaboundingwithmammiferousremains，whichhavenotasyetbeenexaminedbyProfessorOwen，butwhichincludesomelarge，butmostlysmall，speciesofPachydermata，Edentata，andRodentia。Fromtheappearanceofthepale-coloured，fine-grainedbeds，IwasinclinedtobelievethattheycorrespondedwiththeupperbedsoftheS。Cruz;butProfessorEhrenberg，whohasexaminedsomeofthespecimens，informsmethattheincludedmicroscopicalorganismsarewhollydifferent，beingfreshandbrackish-waterforms。HencethetwotothreehundredfeetplainatPortGallegosisofunknownage，butprobablyofsubsequentorigintothegreatPatagoniantertiaryformation。

EASTERNTIERRADELFUEGO。

Judgingfromtheheight，thegeneralappearance，andthewhitecolourofthepatchesvisibleonthehillsides，theuppermostplain，bothonthenorthandwesternsideoftheStraitofMagellan，andalongtheeasterncoastofTierradelFuegoasfarsouthasnearPortSt。Polycarp，probablybelongstothegreatPatagoniantertiaryformation，Thesehighertable-

rangesarefringedbylow，irregular，extensiveplains，belongingtotheboulderformation(Describedinthe“GeologicalTransactions“volume6page415。)，andcomposedofcoarseunstratifiedmasses，sometimesassociated(asnorthofC。Virgin’s)withfine，laminated，muddysandstones。ThecliffsinSebastianBayare200feetinheight，andarecomposedoffinesandstones，oftenincurvilinearlayers，includinghardconcretionsofcalcareoussandstone，andlayersofgravel。Inthesebedstherearefragmentsofwood，legsofcrabs，barnaclesencrustedwithcorallinesstillpartiallyretainingtheircolour，imperfectfragmentsofaPholasdistinctfromanyknownspecies，andofaVenus，approachingverycloselyto，butslightlydifferentinformfrom，theV。lenticularis，aspecieslivingonthecoastofChile。Leavesoftreesarenumerousbetweenthelaminaeofthemuddysandstone;theybelong，asIaminformedbyDr。J。D。Hooker，tothreespeciesofdeciduousbeech，differentfromthetwospecieswhichcomposethegreatproportionoftreesinthisforest-cladland。(“BotanyoftheAntarcticVoyage“page212。)Fromthesefactsitisdifficulttoconjecture，whetherwehereseethebasalpartofthegreatPatagonianformation，orsomelaterdeposit。

SUMMARYONTHEPATAGONIANTERTIARYFORMATION。

Fouroutofthesevenfossilshells，fromSt。FeinEntreRios，werefoundbyM。d’OrbignyinthesandstoneoftheRioNegro，andbymeatSanJosef。

ThreeoutofthesixfromSanJosefareidenticalwiththosefromPortDesireandS。Julian，whichtwoplaceshavetogetherfifteenspecies，outofwhichthreearecommontoboth。SantaCruzhasseventeenspecies，outofwhichfivearecommontoPortDesireandS。Julian。Consideringthedifferenceinlatitudebetweentheseseveralplaces，andthesmallnumberofspeciesaltogethercollected，namelythirty-six，Iconceivetheaboveproportionalnumberofspeciesincommon，issufficienttoshowthatthelowerfossiliferousmassbelongsnearly，Idonotsayabsolutely，tothesameepoch。Whatthisepochmaybe，comparedwiththeEuropeantertiarystages，M。d’Orbignywillnotpretendtodetermine。Thethirty-sixspecies(includingthosecollectedbymyselfandbyM。d’Orbigny)areallextinct，oratleastunknown;butitshouldbeborneinmind，thatthepresentcoastconsistsofshingle，andthatnoone，Ibelieve，hasdredgedhereforshells;henceitisnotimprobablethatsomeofthespeciesmayhereafterbefoundliving。Somefewofthespeciesarecloselyrelatedwithexistingones;thisisespeciallythecase，accordingtoM。d’OrbignyandMr。

Sowerby，withtheFususPatagonicus;and，accordingtoMr。Sowerby，withthePyrula，theVenusmeridionalis，theCrepidulagregaria，andtheTurritellaambulacrum，andT。Patagonica。Atleastthreeofthegenera，namely，Cucullaea，Crassatella，and(asdeterminedbyMr。Sowerby)

Struthiolaria，arenotfoundinthisquarteroftheworld;andTrigonoceliaisextinct。Theevidencetakenaltogetherindicatesthatthisgreattertiaryformationisofconsiderableantiquity;butwhentreatingoftheChileanbeds，Ishallhavetoreferagaintothissubject。

Thewhitepumiceousmudstone，withitsabundantgypsum，belongstothesamegeneralepochwiththeunderlyingfossiliferousmass，asmaybeinferredfromtheshellsincludedintheintercalatedlayersatNuevoGulf，S。

Julian，andS。Cruz。Outofthetwenty-sevenmarinemicroscopicstructuresfoundbyProfessorEhrenberginthespecimensfromS。JulianandPortDesire，tenarecommontothesetwoplaces：thethreefoundatNuevoGulfaredistinct。Ihaveminutelydescribedthisdeposit，fromitsremarkablecharactersanditswideextension。FromCoyInlettoPortDesire，adistanceof230miles，itiscertainlycontinuous;andIhavereasontobelievethatitlikewiseextendstotheRioChupat，NuevoGulf，andSanJosef，adistanceof570miles：wehave，also，seenthatasinglelayeroccursattheRioNegro。AtPortS。Julianitisfromeighttoninehundredfeetinthickness;andatS。Cruzitextends，withaslightlyalteredcharacter，uptotheCordillera。Fromitsmicroscopicstructure，andfromitsanalogywithotherformationsinvolcanicdistricts，itmustbeconsideredasoriginallyofvolcanicorigin：itmayhavebeenformedbythelong-continuedattritionofvastquantitiesofpumice，orjudgingfromthemannerinwhichthemassbecomes，inascendingthevalleyofS。Cruz，dividedintovariouslycolouredlayers，fromthelong-continuederuptionofcloudsoffineashes。Ineithercase，wemustconclude，thatthesouthernvolcanicorificesoftheCordillera，nowinadormantstate，wereataboutthisperiodoverawidespace，andforagreatlengthoftime，inaction。

Wehaveevidenceofthisfact，inthelatitudeoftheRioNegro，inthesandstone-conglomeratewithpumice，anddemonstrativeproofofit，atS。

Cruz，inthevastdelugesofbasalticlava：atthissametertiaryperiod，also，thereisdistinctevidenceofvolcanicactioninWesternBandaOriental。

ThePatagoniantertiaryformationextendscontinuously，judgingfromfossilsalone，fromS。CruztoneartheRioColorado，adistanceofabovesixhundredmiles，andreappearsoverawideareainEntreRiosandBandaOriental，makingatotaldistanceof1，100miles;butthisformationundoubtedlyextends(thoughnofossilswerecollected)farsouthoftheS。

Cruz，and，accordingtoM。d’Orbigny，120milesnorthofSt。Fe。AtS。Cruzwehaveseenthatitextendsacrossthecontinent;beingonthecoastabouteighthundredfeetinthickness(andrathermoreatS。Julian)，andrisingwiththecontemporaneouslava-streamstoaheightofaboutthreethousandfeetatthebaseoftheCordillera。Itrests，whereveranyunderlyingformationcanbeseen，onplutonicandmetamorphicrocks。IncludingthenewerPampeandeposit，andthosestratainEasternTierradelFuegoofdoubtfulage，aswellastheboulderformation，wehavealineofmorethantwenty-sevendegreesoflatitude，equaltothatfromtheStraitsofGibraltartothesouthofIceland，continuouslycomposedoftertiaryformations。Throughoutthisgreatspacethelandhasbeenupraised，withoutthestratahavingbeeninasingleinstance，asfarasmymeansofobservationwent，unequallytiltedordislocatedbyafault。

TERTIARYFORMATIONSONTHEWESTCOAST。

CHONOSARCHIPELAGO。

Thenumerousislandsofthisgroup，withtheexceptionofLemus，Ypun，consistofmetamorphicschists;thesetwoislandsareformedofsoftishgreyandbrown，fusible，oftenlaminatedsandstones，containingafewpebbles，fragmentsofblacklignite，andnumerousmammillatedconcretionsofhardcalcareoussandstone。OutoftheseconcretionsatYpun(latitude40

degrees30minutesS。)，Iextractedthefourfollowingextinctspeciesofshells：——

1。Turritellasuturalis，G。B。Sowerby(alsoNavidad)。

2。Sigaretussubglobosus，G。B。Sowerby(alsoNavidad)。

3。Cytheraea(？)sulculosa(？)，G。B。Sowerby(alsoChiloeandHuafo？)。

4。Voluta，fragmentsof。

Inthenorthernpartsofthisgrouptherearesomecliffsofgravelandoftheboulderformation。Inthesouthernpart(atP。AndresinTresMontes)，thereisavolcanicformation，probablyoftertiaryorigin。Thelavasattainathicknessoffromtwotothreehundredfeet;theyareextremelyvariableincolourandnature，beingcompact，orbrecciated，orcellular，oramygdaloidalwithzeolite，agateandbole，orporphyriticwithglassyalbiticfeldspar。Thereisalsomuchimperfectrubblypitchstone，withtheintersticeschargedwithpowderycarbonateoflimeapparentlyofcontemporaneousorigin。Theselavasareconformablyassociatedwithstrataofbrecciaandofbrowntuffcontaininglignite。Thewholemasshasbeenbrokenupandtiltedatanangleof45degrees，byaseriesofgreatvolcanicdikes，oneofwhichwasthirtyyardsinbreadth。Thisvolcanicformationresemblesone，presentlytobedescribed，inChiloe。

HUAFO。

ThisislandliesbetweentheChonosandChiloegroups：itisabouteighthundredfeethigh，andperhapshasanucleusofmetamorphicrocks。ThestratawhichIexaminedconsistedoffine-grainedmuddysandstones，withfragmentsofligniteandconcretionsofcalcareoussandstone。Icollectedthefollowingextinctshells，ofwhichtheTurritellawasingreatnumbers：——

1。Bullacosmophila，G。B。Sowerby。

2。Pleurotomasubaequalis，G。B。Sowerby。

3。Fususcleryanus，d’Orbigny，“VoyagePal。”(alsoatCoquimbo)。

4。Tritonleucostomoides，G。B。Sowerby。

5。TurritellaChilensis，G。B。Sowerby(alsoMocha)。

6。Venus，probablyadistinctspecies，butveryimperfect。

7。Cytheraea(？)sulculosa(？)，probablyadistinctspecies，butveryimperfect。

8。Dentaliummajus，G。B。Sowerby。

CHILOE。

Thisfineislandisaboutonehundredmilesinlength。Theentiresouthernpart，andthewholewesterncoast，consistsofmica-schist，whichlikewiseisseenintheravinesoftheinterior。Thecentralmountainsrisetoaheightof3，000feet，andaresaidtobepartlyformedofgraniteandgreenstone：therearetwosmallvolcanicdistricts。Theeasterncoast，andlargepartsofthenorthernextremityoftheislandarecomposedofgravel，theboulderformation，andunderlyinghorizontalstrata。ThelatterarewelldisplayedfortwentymilesnorthandsouthofCastro;theyvaryincharacterfromcommonsandstonetofine-grained，laminatedmudstones：allthespecimenswhichIexaminedareeasilyfusible，andsomeofthebedsmightbecalledvolcanicgrit-stones。TheselatterstrataareperhapsrelatedtoamassofcolumnartrachytewhichoccursbehindCastro。Thesandstoneoccasionallyincludespebbles，andmanyfragmentsandlayersoflignite;ofthelatter，someareapparentlyformedofwoodandothersofleaves：onelayerontheN。W。sideofLemuyisnearlytwofeetinthickness。Thereisalsomuchsilicifiedwood，bothcommondicotyledonousandconiferous：asectionofonespecimeninthedirectionofthemedullaryrayshas，asIaminformedbyMr。R。Brown，thediscsinadoublerowplacedalternately，andnotoppositeasinthetrueAraucaria。Ifoundmarineremainsonlyinonespot，insomeconcretionsofhardcalcareoussandstone：inseveralotherdistrictsIhaveobservedthatorganicremainswereexclusivelyconfinedtosuchconcretions;arewetoaccountforthisfact，bythesuppositionthattheshellslivedonlyatthesepoints，orisitnotmoreprobablethattheirremainswerepreservedonlywhereconcretionswereformed？Theshellshereareinabadstate，theyconsistof：——

1。Tellinides(？)oblonga，G。B。Sowerby(asolenellainM。d’Orbigny’sopinion)。

2。Naticastriolata，G。B。Sowerby。

3。Natica(？)pumila，G。B。Sowerby。

4。Cytheraea(？)sulculosa，G。B。Sowerby(alsoYpunandHuafo？)。

Atthenorthernextremityoftheisland，nearS。Carlos，thereisalargevolcanicformation，betweenfiveandsevenhundredfeetinthickness。Thecommonestlavaisblackish-greyorbrown，eithervesicular，oramygdaloidalwithcalcareoussparandbole：mostevenofthedarkestvarietiesfuseintoapale-colouredglass。Thenextcommonestvarietyisarubbly，rarelywellcharacterisedpitchstone(fusingintoawhiteglass)whichpassesinthemostirregularmannerintostonygreylavas。Thispitchstone，aswellassomepurpleclaystoneporphyry，certainlyflowedintheformofstreams。

Thesevariouslavasoftenpass，ataconsiderabledepthfromthesurface，inthemostabruptandsingularmannerintowacke。Greatmassesofthesolidrockarebrecciated，anditwasgenerallyimpossibletodiscoverwhethertherecementingprocesshadbeenanigneousoraqueousaction。(Inacliffofthehardestfragmentarymass，Ifoundseveraltortuous，verticalveins，varyinginthicknessfromafewtenthsofaninchtooneinchandahalf，ofasubstancewhichIhavenotseendescribed。Itisglossy，andofabrowncolour;itisthinlylaminated，withthelaminaetransparentandelastic;itisalittleharderthancalcareousspar;itisinfusibleundertheblowpipe，sometimesdecrepitates，givesoutwater，curlsup，blackens，andbecomesmagnetic。Boraxeasilydissolvesaconsiderablequantityofit，andgivesaglasstingedwithgreen。Ihavenoideawhatitstruenatureis。Onfirstseeingit，Imistookitforlignite！)Thebedsareobscurelyseparatedfromeachother;theyaresometimespartedbyseamsoftuffandlayersofpebbles。Inoneplacetheyrestedon，andinanotherplacewerecappedby，tuffsandgirt-stones，apparentlyofsubmarineorigin。

TheneighbouringpeninsulaofLacuyisalmostwhollyformedoftufaceousdeposits，connectedprobablyintheiroriginwiththevolcanichillsjustdescribed。Thetuffsarepale-coloured，alternatingwithlaminatedmudstonesandsandstones(alleasilyfusible)，andpassingsometimesintofine-grainedwhitebedsstrikinglyresemblingthegreatupperinfusorialdepositofPatagonia，andsometimesintobrecciolaswithpiecesofpumiceinthelaststageofdecay;theseagainpassintoordinarycoarsebrecciasandconglomeratesofhardrocks。Withinveryshortdistances，someofthefinertuffsoftenpassedintoeachotherinapeculiarmanner，namely，byirregularpolygonalconcretionsofonevarietyincreasingsomuchandsosuddenlyinsize，thatthesecondvariety，insteadofanylongerformingtheentiremass，wasleftmerelyinthinveinsbetweentheconcretions。Inastraightlineofcliffs，atPointTenuy，Iexaminedthefollowingremarkablesection(Figure19)：——

(FIGURE19。)

Onthelefthand，thelowerpart(AA)consistsofregular，alternatingstrataofbrowntuffsandgreenishlaminatedmudstone，gentlyinclinedtotheright，andconformablycoveredbyamass(Bleft)ofawhite，tufaceousandbrecciolateddeposit。Ontherighthand，thewholecliff(BBright)

consistsofthesamewhitetufaceousmatter，whichonthissidepresentsscarcelyatraceofstratification，buttotheleftbecomesverygraduallyandratherindistinctlydividedintostrataquiteconformablewiththeunderlyingbeds(AA)：moreover，afewhundredyardsfurthertotheleft，wherethesurfacehasbeenlessdenuded，thetufaceousstrata(Bleft)areconformablycoveredbyanothersetofstrata，liketheunderlyingones(AA)

ofthissection。Inthemiddleofthediagram，thebeds(AA)areseentobeabruptlycutoff，andtoabutagainstthetufaceousnon-stratifiedmass;

butthelineofjunctionhasbeenaccidentallynotrepresentedsteepenough，forIparticularlynoticedthatbeforethebedshadbeentiltedtotheright，thislinemusthavebeennearlyvertical。Itappearsthatacurrentofwatercutforitselfadeepandsteepsubmarinechannel，andatthesametimeorafterwardsfilleditupwiththetufaceousandbrecciolatedmatter，andspreadthesameoverthesurroundingsubmarinebeds;thematterbecomingstratifiedinthesemoredistantandlesstroubledparts，andbeingmoreoversubsequentlycoveredupbyotherstrata(likeAA)notshowninthediagram。Itissingularthatthreeofthebeds(ofAA)areprolongedintheirproperdirection，asrepresented，beyondthelineofjunctionintothewhitetufaceousmatter：theprolongedportionsoftwoofthebedsarerounded;inthethird，theterminalfragmenthasbeenpushedupwards：howthesebedscouldhavebeenleftthusprolonged，Iwillnotpretendtoexplain。Inanothersectionontheoppositesideofapromontory，therewasatthefootofthissamelineofjunction，thatisatthebottomoftheoldsubmarinechannel，apileoffragmentsofthestrata(AA)，withtheirintersticesfilledupwithwhitetufaceousmatter：thisisexactlywhatmighthavebeenanticipatedundersuchcircumstances。

(FIGURE20。GROUNDPLANSHOWINGTHERELATIONBETWEENVEINSAND

CONCRETIONARYZONESINAMASSOFTUFF。)

ThevarioustufaceousandotherbedsatthisnorthernendofChiloeprobablybelongtoaboutthesameagewiththosenearCastro，andtheycontain，asthere，manyfragmentsofblackligniteandofsilicifiedandpyritouswood，oftenembeddedclosetogether。Theyalsocontainmanyandsingularconcretions：someareofhardcalcareoussandstone，inwhichitwouldappearthatbrokenvolcaniccrystalsandscalesofmicahavebeenbetterpreserved(asinthecaseoftheorganicremainsnearCastro)thaninthesurroundingmass。Otherconcretionsinthewhitebrecciolaareofahard，ferruginous，yetfusible，nature;theyareasroundascannon-balls，andvaryfromtwoorthreeinchestotwofeetindiameter;theirinsidesgenerallyconsisteitheroffine，scarcelycoherentvolcanicsand(Thefrequenttendencyinirontoformhollowconcretionsorshellcontainingincoherentmatterissingular;D’Aubuisson(“TraitedeGeogn。”tome1page318)remarksonthiscircumstance。)，orofanargillaceoustuff;inthislattercase，theexternalcrustwasquitethinandhard。Someofthesesphericalballswereencircledinthelineoftheirequators，byanecklace-likerowofsmallerconcretions。Againtherewereotherconcretions，irregularlyformed，andcomposedofahard，compact，ash-

colouredstone，withanalmostporcelainousfracture，adhesivetothetongue，andwithoutanycalcareousmatter。Thesebedsare，also，interlacedbymanyveins，containinggypsum，ferruginousmatter，calcareousspar，andagate。Itwashereseenwithremarkabledistinctness，howintimatelyconcretionaryactionandtheproductionoffissuresandveinsarerelatedtogether。Figure20isanaccuraterepresentationofahorizontalspaceoftuff，aboutfourfeetlongbytwoandahalfinwidth：thedoublelinesrepresentthefissurespartiallyfilledwithoxideofironandagate：thecurvilinearlinesshowthecourseoftheinnumerable，concentric，concretionaryzonesofdifferentshadesofcolourandofcoarsenessintheparticlesoftuff。Thesymmetryandcomplexityofthearrangementgavethesurfaceanelegantappearance。Itmaybeseenhowobviouslythefissuresdetermine(orhavebeendeterminedby)theshape，sometimesofthewholeconcretion，andsometimesonlyofitscentralparts。Thefissuresalsodeterminethecurvaturesofthelongundulatingzonesofconcretionaryaction。Fromthevaryingcompositionoftheveinsandconcretions，theamountofchemicalactionwhichthemasshasundergoneissurprisinglygreat;anditwouldlikewiseappearfromthedifferenceinsizeintheparticlesoftheconcretionaryzones，thatthemass，also，hasbeensubjectedtointernalmechanicalmovements。

InthepeninsulaofLacuy，thestrataoverawidthoffourmileshavebeenupheavedbythreedistinct，andsomeotherindistinct，linesofelevation，rangingwithinapointofnorthandsouth。Oneline，abouttwohundredfeetinheight，isregularlyanticlinal，withthestratadippingawayonbothsides，atanangleof15degrees，fromacentral“valleyofelevation，“

aboutthreehundredyardsinwidth。Asecondnarrowsteepridge，onlysixtyfeethigh，isuniclinal，thestratathroughoutdippingwestward;thoseonbothflanksbeinginclinedatanangleoffromtentofifteendegrees;

whilstthoseontheridgedipinthesamedirectionatanangleofbetweenthirtyandfortydegrees。Thisridge，tracednorthwards，diesaway;andthebedsatitsterminalpoint，insteadofdippingwestward，areinclined12

degreestothenorth。Thiscaseinterestedme，asbeingthefirstinwhichIfoundinSouthAmerica，formationsperhapsoftertiaryorigin，brokenbylinesofelevation。

VALDIVIA：ISLANDOFMOCHA。

TheformationsofChiloeseemtoextendwithnearlythesamecharactertoValdivia，andforsomeleaguesnorthwardofit：theunderlyingrocksaremicaceousschists，andarecoveredupwithsandstoneandothersedimentarybeds，including，asIwasassured，inmanyplaceslayersoflignite。IdidnotlandonMocha(latitude38degrees20minutes)，butMr。Stokesbroughtmespecimensofthegrey，fine-grained，slightlycalcareoussandstone，preciselylikethatofHuafo，containingligniteandnumerousTurritellae。

Theislandisflattopped，1，240feetinheight，andappearslikeanoutlierofthesedimentarybedsonthemainland。Thefewshellscollectedconsistof：——

1。TurritellaChilensis，G。B。Sowerby(alsoatHuafo)。

2。Fusus，veryimperfect，somewhatresemblingF。subreflexusofNavidad，butprobablydifferent。

3。Venus，fragmentsof。

CONCEPCION。

SailingnorthwardfromValdivia，thecoast-cliffsareseen，firsttoassumeneartheR。Tolten，andthencefor150milesnorthward，tobecontinuedwiththesamemineralogicalcharacters，immediatelytobedescribedatConcepcion。Iheardinmanyplacesofbedsoflignite，someofitfineandglossy，andlikewiseofsilicifiedwood;neartheToltenthecliffsarelow，buttheysoonriseinheight;andthehorizontalstrataareprolonged，withanearlylevelsurface，untilcomingtoamoreloftytractbetweenpointsRumenaandLavapie。Herethebedshavebeenbrokenupbyatleasteightornineparallellinesofelevation，rangingE。orE。N。E。andW。orW。S。W。Theselinescanbefollowedwiththeeyemanymilesintotheinterior;theyarealluniclinal，thestrataineachdippingtoapointbetweenS。andS。S。E。withaninclinationinthecentrallinesofaboutfortydegrees，andintheouteronesofundertwentydegrees。Thisbandofsymmetricallytroubledcountryisabouteightmilesinwidth。

TheislandofQuiriquina，intheBayofConcepcion，isformedofvarioussoftandoftenferruginoussandstones，withbandsofpebbles，andwiththelowerstratasometimespassingintoaconglomeraterestingontheunderlyingmetamorphicschists。Thesebedsincludesubordinatelayersofgreenishimpureclay，softmicaceousandcalcareoussandstones，andreddishfriableearthymatterwithwhitespeckslikedecomposedcrystalsoffeldspar;theyinclude，also，hardconcretions，fragmentsofshells，lignite，andsilicifiedwood。Intheupperparttheypassintowhite，softsedimentsandbrecciolas，verylikethosedescribedatChiloe;asindeedisthewholeformation。AtLirguenandotherplacesontheeasternsideofthebay，therearegoodsectionsofthelowersandstones，whicharegenerallyferruginous，butwhichvaryincharacter，andevenpassintoanargillaceousnature;theycontainhardconcretions，fragmentsoflignite，silicifiedwood，andpebbles(ofthesamerockswiththepebblesinthesandstonesofQuiriquina)，andtheyalternatewithnumerous，oftenverythinlayersofimperfectcoal，generallyoflittlespecificgravity。Themainbedhereisthreefeetthick;andonlythecoalofthisonebedhasaglossyfracture。Anotherirregular，curvilinearbedofbrown，compactlignite，isremarkableforbeingincludedinamassofcoarsegravel。Theseimperfectcoals，whenplacedinaheap，ignitespontaneously。Thecliffsonthissideofthebay，aswellasontheislandofQuiriquina，arecappedwithredfriableearth，which，asstatedintheSecondChapter，isofrecentformation。Thestratificationinthisneighbourhoodisgenerallyhorizontal;butnearLirguenthebedsdipN。W。atanangleof23degrees;

nearConcepciontheyarealsoinclined：atthenorthernendofQuiriquinatheyhavebeentiltedatanangleof30degrees，andatthesouthernendatanglesvaryingfrom15degreesto40degrees：thesedislocationsmusthavetakenplaceunderthesea。

Acollectionofshells，fromtheislandofQuiriquina，hasbeendescribedbyM。d’Orbigny：theyareallextinct，andfromtheirgenericcharacter，M。

d’Orbignyinferredthattheywereoftertiaryorigin：theyconsistof：——

1。ScalariaChilensis，d’Orbigny，“Voyage，PartPal。”

2。NaticaAraucana，d’Orbigny，“Voyage，PartPal。”

3。Naticaaustralis，d’Orbigny，“Voyage，PartPal。”

4。Fususdifficilis，d’Orbigny，“Voyage，PartPal。”

5。Pyrulalongirostra，d’Orbigny，“Voyage，PartPal。”

6。PleurotomaAraucana，d’Orbigny，“Voyage，PartPal。”

7。Cardiumauca，d’Orbigny，“Voyage，PartPal。”

8。Cardiumacuticostatum，d’Orbigny，“Voyage，PartPal。”

9。Venusauca，d’Orbigny，“Voyage，PartPal。”

10。Mactracecileana，d’Orbigny，“Voyage，PartPal。”

11。MactraAraucana，d’Orbigny，“Voyage，PartPal。”

12。ArcaAraucana，d’Orbigny，“Voyage，PartPal。”

13。NuculaLargillierti，d’Orbigny，“Voyage，PartPal。”

14。TrigoniaHanetiana，d’Orbigny，“Voyage，PartPal。”

Duringasecondvisitofthe“Beagle“toConcepcion，Mr。KentcollectedformesomesilicifiedwoodandshellsoutoftheconcretionsinthesandstonefromTome，situatedashortdistancenorthofLirguen。Theyconsistof：——

1。Naticaaustralis，d’Orbigny，“Voyage，PartPal。”

2。MactraAraucana，d’Orbigny，“Voyage，PartPal。”

3。TrigoniaHanetiana，d’Orbigny，“Voyage，PartPal。”

4。Pecten，fragmentsof，probablytwospecies，buttooimperfectfordescription。

5。Baculitesvagina，E。Forbes。

6。Nautilusd’Orbignyanus，E。Forbes。

Besidestheseshells，CaptainBelcherfoundhereanAmmonite，nearlythreefeetindiameter，andsoheavythathecouldnotbringitaway;fragmentsaredepositedatHaslarHospital：healsofoundthesilicifiedvertebraeofsomeverylargeanimal。(“ZoologyofCaptainBeechey’sVoyage“page163。)