SKULL OF THE CROCODILE. 109 



face. These bones, which are called " prefontals," stand 

 in the relation of " neurapophyses" to the rhinencephalic 

 prolongations of the brain commonly but erroneously 

 called "olfactory nerves;" and they form the piers or 

 haunches of a neural arch, which is completed above by 

 a pair of symmetrical bones, 15, called " nasals," which I 

 regard as a divided or bifid neural spine. 



The centrum of this arch is established by ossification 

 in the expanded anterior prolongation of the fibrous cap- 

 sule of the notochord, beyond the termination of its gela- 

 tinous axis. The median portion above specified retains 

 most of the formal characters of the centrum ; but there 

 is a pair of long, slender, symmetrical ossicles, which, 

 from the seat of their original development, and their 

 relative position to the neural arch, must be regarded as 

 also parts of its centrum. And this ossification of the 

 element in question from different centres will be no new 

 or strange character to those who recollect that the ver- 

 tebral body in man and mammalia is developed from three 

 centres. The term "vomer" is applied to the pair of 

 bones, 13, because their special homology with the single 

 median bone, so called in fishes and mammals, is indis- 

 putable; but a portion of the same element of the skull 

 retains its single symmetrical character in the crocodile, 

 and is connate with the enormous pterygoids, 24, between 

 which it is wedged. In some alligators {all. niger) the 

 divided anterior vomer extends far forwards, expands 

 anteriorly, and appears upon the bony palate. 



Almost all the other bones of the head of the crocodile 

 are adjusted so as to constitute four inverted arches. 

 These are the haemal arches of the four segments or ver- 

 tebrae, of which the neural arches have been just described. 

 But they have been the seat of much greater modifica- 

 10 



