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[1] 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.[2]
During these grand periods of lacustrine mammalia, in which but few of the present genera of terrestrial carnivore
- ↑ The small Opossums in the oolite formation at Stonesfield, near Oxford, are the only land mammalia whose bones have been yet discovered in any strata more ancient than the tertiary.
- ↑ One of these, found by Mr. Spencer in the London clay of the Isle of Sheppy, is engraved, Pl. 25', Fig. 1. Crocodiles of this kind have been fund in the chalk of Meudon, in the plastic clay of Auteuil, in the London day, in the gypsum of Mont Martre, and in the lignites of Provence.
The modern broad-nosed Crocodileans, though they have the power to capture mammalia, are not limited to this kind of prey; they feed largely also on fishes, and occasionally on birds. This omnivorous character of the existing Crocodilean family, seems adapted no the present general diffusion of more varied kinds of food, than existed when the only form of the beak in this family was fitted, like that of the Gavial, to feed chiefly on Fishes.
