18 FOSSIL REPTILIA OP THE 



not occupied by the prey is filled with the fluid in which the mammal is being dragged 

 and drowned. " The closure of the exterior nostrils "^ would not prevent the water 

 entering the ' glottis.' A special arrangement is requisite for this purpose, and such 

 arrangement, as it exists in Neozoic Crocodiles, is incompatible with the relative position 

 of " the posterior nares " and the glottis in the Mesozoic Crocodiles. The question is, 

 with a closure of the external nostrils and the exclusion of water admitted by the mouth 

 into the nasal passage, how is the water to be prevented from getting into the windpipe ? 

 We know how this is effected in the Cetaceans ; and modern Crocodiles have as efficient 

 a mechanism to the same end though on a different plan, but requiring a size and 

 position of the palatonares which constitutes one of the best marked cranial characters 

 differentiating the Mesozoic and Neozoic Crocodilia. 



In all the Crocodiles contemporary with "large and active mammals "^ there is a 

 double valvular structure at the back of the mouth, which prevents the water having 

 access to the mouth, from entering either the hinder nostril or the glottis. A mem- 

 branous and fleshy fold hangs, like a curtain, from the hind border of the roof of the 

 mouth, and answers to our ' velum palati :' the other valve is peculiarly crocodilian ; it is 

 a broad, gristly plate, which rises from the root of the tongue, carrying with it a covering 

 of the lingual integument ; and, when the palatal valve is applied to it, they form 

 together a complete partition wall, closing the back of the mouth, between which and 

 " the posterior nares " it is situated, shutting off" both the latter aperture and the glottis 

 from the mouth. 



To make this mechanism available, the hind nostril is reduced in size, and such 

 reduction is shown in the skull. The palatonaris is also placed far back, and its plane 

 instead of being horizontal is tilted up at the angle which makes the operation of the 

 two parts or folding doors of the partition most effective in closing the oral chamber 

 posteriorly.^ If the submergence of the Crocodile, with its " large mammalian "* prey, 

 should last so long as to render it needful for the reptile to take a fresh breath, it can 

 protrude its prominent snout from the surface of the river, and inhale a current of air 

 which will traverse the long meatus and enter the glottis by the chamber common to 

 nose and windpipe, which is shut off from the mouth by the above-described structures. 

 We have no ground for inferring such from the bony palate in amphiccelian Crocodiles ; 

 the difference in its size and position are such as to have deceived both Bronn and 

 De Blainville as to the position and homology of the palatonares in Teleosaurus} 



The subjects of the present Monograph bear unexpectedly, and in an interesting 

 degree, on another objection, raised during the discussion at the Geological Society of 



^ 'Quart. Jourr.. of Geol. Soc.,' May, 18/8, p. 429. 



2 Loc. cit., p. 425. 



3 'Proceedings of the Zool. Soc.,' October 25th, 1831, p. 139. 

 * lb. ib., p. 426. 



^ ' Abhandlungen iiber die Gavial-artigen Reptilien der Lias-formation,' fol., 1841, pp. 12, 16, 24. 



