ANATOMY OF VERTEBRATES. 



135 



mastoids. The pvemaxillary is either wanting, or it is very small, 

 and represented by its alveolar border only; the maxillaries 

 meeting above it. The alveolar borders of both upper and lower 

 jaws show a regular series of vascular pits or foramina, indica- 

 tive ol the primitive separate matrices, like those of teeth, which 

 laid the foundation in the young animal of the continuous horny 

 coverings of the jaws. 



Temminck's Snapper ( Chelonura Temminckii) is remarkaljle for 

 the upper convexity and enormous expanse of the cranium, chiefly 

 due to the temporal fossaj, contrasted with the short and narrow 

 face. In a fossil chelonian from the Portland stone ( Ch. planiceps) 

 and in another from the Clialk ( Ch. pulchriceps) the nasals Avere 

 distinct from the prefrontals, wliich is a rare exce2)tion in existing 

 species. 



93 



Hro 



Side view of cranial vcrtcbnTS and Eeusc-capsnles, Crocodile 



§ 32. Skull of Crocodilia. — Passing next to the skull of the 

 Crocodile, we find the first difference in the less complex condition 

 of the epencephahc arch, fig. 9.3, n i, which consists of four, instead 

 of, as in the Fish and Turtle, six bones. The basioccipital, figs. 93 

 and 94, i, presents, Hke the centrums of the trunk, a convexity at 

 its posterior articular surface ; but its anterior one, like the hind- 

 most centrum of the sacrum, unites with the next centrum in ad- 

 vance, ib. 5, by a flat rough sutural surface. Like most of the cen- 

 trums in the neck and beginning of the back, that of the occiput 

 developes a hypapophysis, but tliis descending process is longer and 

 laro-er. The exoccipitals, ib. 2, articulate suturally, like the neur- 

 apophyses of the trunk, with the upper and lateral parts of their 



