CROCODILIA. 



Kg. -9 



17 



Disarticulated bones of the Skull of an Alligator, N I to iv the neural arches ; 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, Ni, Hi; •> 



Parietal vertebra, N n, H n ; 



\ Fi°- 9 

 Frontal vertebra, N in, H in ; / & ' 



Nasal vertebra, N iv, H iv. 

 These segments are subdivided into the neural arches, called 



Epencephalic arch (l 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 



