68 The Alligator and Its Allies 



surface of the basisphenoid is the pituitary fossa, 

 not seen, of course, in this view of the skull. 



The alisphenoids (crossed by the dotted line from 

 V) are a pair 01 very irregular bones that form most 

 of the antero-lateral walls of the brain case. They 

 articulate dorsally with the parietal, frontal, and 

 postfrontal; ventrally with the basisphenoid 

 and pterygoid; and posteriorly with the quadrate 

 and some of the otic bones not visible in this view. 

 Between it and the quadrate, plainly visible in this 

 view, is a large opening, the foramen ovale (V), 

 through which, according to Reynolds, the tri- 

 geminal nerve passes. In the middle line, directly 

 under the frontal bone, is an opening between the 

 anterior wings of the two alisphenoids, for the exit 

 of the optic nerves. Ventrad and caudad to this 

 opening, and sometimes continuous with it, is 

 another large foramen, just dorsad to the rostrum, 

 for the exit, according to Reynolds, of the oculo- 

 motor and abducens nerves. Projecting caudad 

 is seen the rounded condylar part of the basi- 

 occipital (14) to be described later, and dorso- 

 cephalad to this is a part of the exoccipital (13) 

 in which four foramina may be seen ; of the dorsal 

 three the one nearest the condyle and foramen 

 magnum is for the exit (Reynolds) of the hypo- 

 glossal nerve (XII); slightly dorso-cephalad to 

 this is one for the vagus nerve (X) ; between these 

 two is a very small one for a vein ; the largest and 

 ventrally located foramen is for the entrance of the 



