The beds including the above fossil remains stand only from fifteen
to twenty feet above the level of high water; and hence the
elevation of the land has been small (without there has been an
intercalated period of subsidence, of which we have no evidence)
since the great quadrupeds wandered over the surrounding plains;
and the external features of the country must then have been very
nearly the same as now. What, it may naturally be asked, was the
character of the vegetation at that period; was the country as
wretchedly sterile as it now is? As so many of the co-embedded
shells are the same with those now living in the bay, I was at
first inclined to think that the former vegetation was probably
similar to the existing one; but this would have been an erroneous
inference, for some of these same shells live on the luxuriant
coast of Brazil; and generally, the characters of the inhabitants
of the sea are useless as guides to judge of those on the land.
Nevertheless, from the following considerations, I do not believe
that the simple fact of many gigantic quadrupeds having lived on
the plains round Bahia Blanca, is any sure guide that they formerly
were clothed with a luxuriant vegetation: I have no doubt that the
sterile country a little southward, near the Rio Negro, with its
scattered thorny trees, would support many and large quadrupeds.
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