CROCODILIA. 



Fig. .9 



Hiu 



Disarticulated bones of the Skull of an Alligator, N i to rv the neural arches j H i to iv the haemal arches 



and appendages. 



The bones of the endo- skeleton of the head form naturally four segments, called 

 Occipital vertebra, N I, H I ; \ 



Fig. 9. 



Parietal vertebra, N n, H n ; 



Frontal vertebra, N m, H in ; 



Nasal vertebra, N iv, H iv. 

 These segments are subdivided into the neural arches, called 



Epencephalic arch (1 basioccipital, 2 exoccipital, 3 superoccipital, 4 connate 

 paroccipital) ; 



Mesencephalic arch (5 basisphenoid, 6 alisphenoid, 7 parietal, 8 mastoid) ; 



Prosencephalic arch (9 presphenoid, 10 orbitosphenoid, 11 frontal, 12 post- 

 frontal) ; 



Rhinencephalic arch (13 vomer, 14 prefrontal, 15 nasal) : 

 and into the haemal arches and their appendages, called 



Maxillary arch (20 palatine, 21 maxillary, 22 premaxillary) and appendages 

 (24 pterygoid, 24' ectopterygoid, 26 malar, 27 squamosal) ; 



Mandibular arch (28 tympanic, 29—32 mandible) ; 



3 



