PuntaAltaissituatedaboutthirtymileshigheruponthenorthernsideofthissamebay：itconsistsofasmallplain，betweentwentyandthirtyfeetinheight，cutoffontheshorebyalineoflowcliffsaboutamileinlength，representedinFigure15withitsverticalscalenecessarilyexaggerated。ThelowerbedAismoreextensivethantheupperones;itconsistsofstratifiedgravelorconglomerate，cementedbycalcareo-
arenaceousmatter，andisdividedbycurvilinearlayersofpinkishmarl，ofwhichsomearepreciselyliketosca-rock，andsomemoresandy。Thebedsarecurvilinear，owingtotheactionofcurrents，anddipindifferentdirections;theyincludeanextraordinarynumberofbonesofgiganticmammifersandmanyshells。Thepebblesareofconsiderablesize，andareofhardsandstone，andofquartz，likethatoftheVentana：therearealsoafewwell-roundedmassesoftosca-rock。
ThesecondbedBisaboutfifteenfeetinthickness，buttowardsbothextremitiesofthecliffnotincludedinthediagramiteitherthinsoutanddiesaway，orpassesinsensiblyintoanoverlyingbedofgravel。Itconsistsofred，toughclayeymud，withminutelinearcavities;itismarkedwithfainthorizontalshadesofcolour;itincludesafewpebbles，andrarelyaminuteparticleofshell：inonespot，thedermalarmourandafewbonesofaDasypoidquadrupedwereembeddedinit：itfillsupfurrowsintheunderlyinggravel。Withtheexceptionofthefewpebblesandparticlesofshells，thisbedresemblesthetruePampeanmud;butitstillmorecloselyresemblestheclayeyflatsmentionedintheFirstChapter
separatingthesuccessivelyrisingparallelrangesofsand-dunes。
ThebedCisofstratifiedgravel，likethelowestone;itfillsupfurrowsintheunderlyingredmud，andissometimesinterstratifiedwithit，andsometimesinsensiblypassesintoit;astheredmudthinsout，thisuppergravelthickens。Shellsaremorenumerousinitthaninthelowergravel;