chap. xi. Bahia B lancet. 329 



as they do on the present coast. These beds, from the 

 number of littoral species, must have been accumulated 

 in shallow water ; but not, judging from the stratifica- 

 tion of the gravel and the layers of marl, on a beach. 

 From the manner in which the red clay fills up furrows 

 in the underlying gravel, and is in some parts itself 

 furrowed by the overlying gravel, whilst in other parts 

 it either insensibly passes into, or alternates with, this 

 upper gravel, we may infer several local changes in the 

 currents, perhaps caused by slight changes, up or down, 

 in the level of the land. By the elevation of these 

 beds, to which period the alluvial mantle with pumice- 

 pebbles, land and sea-shells belongs, the plain of Punta 

 Alta, from twenty to thirty feet in height, was formed. 

 In this neighbourhood there are other and higher sea- 

 formed plains and lines of cliffs in the Pampean forma- 

 tion worn by the denuding action of the waves at 

 different levels. Hence we can easily understand the 

 presence of rounded masses of tosca-rock in this lowest 

 plain ; and likewise, as the cliffs at Monte Hermoso 

 with their mammiferous remains stand at a higher level, 

 the presence of the one much-rolled fragment of bone 

 which was as black as jet : possibly some few of the 

 other much-rolled bones may have been similarly de- 

 rived, though I saw only the one fragment, in the same 

 condition with those from Monte Hermoso. M. d'Or- 

 bigny has suggested 1 that all these mammiferous 

 remains may have been washed out of the Pampean 

 formation, and afterwards redeposited together with 

 the recent shells. Undoubtedly it is a marvellous fact 

 that these numerous gigantic quadrupeds, belonging, 

 with the exception of the JEquus curvidens, to seven 

 extinct genera, and one, namely, the Toxodon, not 

 falling into any existing family, should have co-existed 

 1 « Voyage, Part. Geolog.' p. 49. 



