Miscellaneous. 463 



opened above the surface of the water. The border of the orbit is 

 raised for that purpose, so as to bring the eye to the summit of the 

 head in modern Gavials and Crocodiles, — conditions for speedy pro- 

 gress through water being sacrificed for other advantages, necessitated 

 perhaps by the more formidable enemies that modern Crocodilia 

 have to encounter, as compared with ancient ones, and by the fre- 

 quent position of those enemies on dry land. With the Teleosauriy 

 the danger would come most probably exclusively from Cetiosauri or 

 huge Ichthyosauri cleaving the same element. Accordingly the eyes 

 looked outwards rather than upwards, and the outer surface of the 

 head was evenly shaped and expanded to concur with other modifi- 

 cations of their frame for swift natation. 



As we discern, therefore, in the upraised orbits of modern Croco- 

 dilia, their advantage in being able to peer abroad and scan the banks 

 of their stream with the least possible exposure of their head, and 

 connect that advantage with the position of the formidable enemy to 

 which they are now exposed ; so, likewise, we discern in the shortening 

 and expansion of their jaws, the enlargement and strengthening of 

 their teeth, and the development of certain of these into canine- 

 shaped tusks, a relation to a source of food in the coexisting Mam- 

 mals, which would seem not to have existed for the Teleosauri ; if, 

 indeed, large quadrupeds of the Mammalian class coexisted at all on 

 the land washed by the ancient seas in which the Teleosauri seem 

 habitually to have dwelt. 



The pterygoids in modern Crocodiles are so developed in breadth 

 and length as to carry back the inner nostril much beyond its posi- 

 tion in Teleosauri ; and the pterygoids are united together to such an 

 extent as much to reduce the size of that aperture. This contracted 

 posterior nostril is associated in modern Crocodiles with a peculiar 

 development of the base of the tongue and soft palate, which shuts 

 off all communication between the cavity of the mouth and the air- 

 passage from the nose to the windpipe. Hence, while the crocodile 

 is holding under water a struggling and drowning quadruped, the 

 water in the mouth of the crocodile cannot flow into the glottis ; 

 and, if the raised nostril on the upper surface of the skull be pro- 

 truded, air can be inhaled into the lungs without any need for relaxing 

 the grip of the prey and closing the mouth. Supposing the Teleo- 

 sauri to have subsisted exclusively on fishes or aquatic animals, as the 

 gavial-like length and slenderness of their jaws and their numerous 

 sharp serial teeth would indicate, such departure from type as the 

 pterygoid developments in modern Crocodilia would not be needed ; 

 and we again discern in the latter their relation to the higher forms 

 of animal life with which those Crocodilia are now associated. 



And these indications collaterally bear very significant evidence 

 against the inference, based on the insecurity of negative evidence, 

 that Mammalian life may have been as rife in Oolitic and Liassic times 

 as at present, only not yet discovered. 



