CROCODILES. 



347 



ture, this aperture is thrown further back, so that a line 

 drawn transversely through the grooves for receiving the 4th 

 lower teeth (which in the existing animal would cut the 

 posterior extremity), in the fossil passes through the centre, 

 or rather in front of the centre of the nasal aperture. 



The skulls of the true Crocodile and Cayman differ in the 

 following points. 1. That of the Cayman is less oblong, 

 shorter, and flatter at the muzzle. 2. The 4th tooth of the 

 lower jaw enters into a hole in the upper, instead of a groove 

 as in the true Crocodile. 3. They differ in the number of 

 the teeth. 4. The cranial foramina bounded by the posterior 

 frontal, mastoid, and parietal bones, are smaller, and some- 

 times altogether wanting in the Cayman. 5. The lachrymal 

 and anterior frontal bones descend lower in the Crocodiles 

 than in the Caymans. 6. In the Cayman a part of the vomer 

 is visible in the palate between the maxillaries and the inter- 

 maxillaries. 7. The palatine bones advance more in the 

 palate and are wider in front in the same animal. 8. The 

 posterior nostrils are wider than they are long. 



With regard to the cranial foramina of the fossil, and their 

 proportion relatively to the surrounding bones, we are enabled, 

 by having in our possession a very perfect fragment of the 

 occipital region and that portion of the skull bounded by the 

 orbits, to give the comparative measurements here also ; 

 noting that this fossil is a portion of the skull of an animal 

 of much smaller dimensions than that from which the former 

 measurements were taken. 



It wiU be observed from the above that the fossil and the 

 existing animal of 11 feet very closely correspond in dimen- 

 sions, although the crotaphifce foramina are rather larger, 

 and the width of the bones in their neighbourhood greater in 

 the fossil than in the existing one. This proportional excess 



