Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/196

 Rh have fed chiefly upon them, and if in the existing' family of Crocodiles there be any, that are in » a peculiar degree piscivorous, their form is that we should expect to find in those most ancient fossil genera, whose chief supply of food must have been derived from fishes,

In the living sub-genera of the Crocodilean family, we see the elongated and slender beak of the Gavial of the Ganges, constructed to feed on fishes; whilst the shorter and stronger snout of the broad-nosed Crocodiles and Alligators gives them the power of seizing and devouring quadrupeds, that come to the banks of rivers in hot countries to drink. As there were scarcely any mammalia during the secondary periods, whilst the waters were abundantly stored with fishes, we might, à priori, expect that if any Crocodilean forms had then existed they would most nearly have resembled the modern Gavial. And we have hitherto found only those genera which have elongated beaks, in formations anterior to, and including the chalk; whilst true Crocodiles, with a short and broad snout, like that of the Cayman and the Alligator, appear for the first time in strata of the tertiary periods, in which the remains of mammalia abound.

During these grand periods of lacustrine mammalia, in which but few of the present genera of terrestrial carnivore