104 SKULL OF THE CROCODILE. 



unites with the next centrum in advance by a flat rough 

 " sutural" surface. Like most of the centrums in the neck 

 and beginning of the back, that of the occiput develops 

 a hypapophysis, but this descending process is longer 

 and larger, its base extending over the whole of the under 

 surface of the centrum. It is a character whereby the 

 occipital centrum of a crocodilian reptile may be dis- 

 tinguished from that of a lacertian one ; for in the latter 

 a pair of diverging hypapophyses project from the under 

 surface, as is shown in most recent lizards and in the 

 great extinct mosasaurus. 



The upper and lateral parts of No. 1 present rough 

 sutural surfaces, like those in the centrums of the trunk, 

 for articulating with the " neurapophyses," Nos. 2, 2, 

 which develop short, thick, obtuse, transverse processes, 

 4, 4. The modified or specialized character of the ele- 

 ments of the cranial vertebrse has gained for them special 

 names. The centrum, 1, is called, as in fishes and all 

 other vertebrates, the " basioccipital ;" the neurapophy- 

 ses, 2, 2, are the " exoccipitals ;" the neural spine, 8, is 

 the "superoccipital." The transverse processes, 4, 4, 

 which may combine both diapophyses and paropophyses, 

 are called the " paroccipitals ;" they are never detached 

 bones in the crocodilia, as they are in the chelonia and 

 in most fishes. The exoccipitals perform the usual func- 

 tions of neurapophyses, and, like those of the atlas, meet 

 above the neural canal ; they are perforated to give exit 

 to the vagal and hypoglossal nerves, and protect the 

 sides of the medulla oblongata and cerebellum — the two 

 divisions of the epencephalon. The superoccipital, 3, is 

 broad and flat, like the similarly detached neural spine 

 of the atlas; it advances a little forwards, beyond its sus- 

 taining neurapophyses, to protect the upper surface of 



