192 AMPHIBIOUS SAURIANS. 



have fed chiefly upon them, and if in the existing family of 

 Crocodiles there be any, that are in a pecuHar degree pis- 

 civorous, 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 Alli- 

 gators gives them the power of seizing and devouring quad- 

 rupeds, 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 h priori, expect that if any Croco- 

 dilean 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 ter- 

 tiary periods, in which the remains of mammalia abound.f 



During these grand periods of lacustrine mammalia, in 

 which but few of the present genera of terrestrial carnivora 



* 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. 



t One of these, found by Mr, Spencer in the London clay of (he Isle 

 of Sheppy, is engraved, PI. 25', Fig. 1. Crocodiles of this kind have 

 been found in the chalk of Meudon, in the plastic clay of Auteuil, in the 

 London clay, in the gypsum of Mont Martre, and in the lignites of Pro- 

 vence. 



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 ci)aractcr of 

 the existing Crocodilean family, seems adapted to the present general 

 diffusion of more varied kinds of food, than existed when the only form of 

 the beak ia this family was fitted, like that of the Gavial, to feed cliiefly on 

 Fishes. 



