20 THE MORPHOLOGY OF THE SKULL 



thin and plate-like. It joins the quadrate as described above and from its upper sur- 

 face rises the epipterygoid. 



The epipterygoid : The epipterygoid is the only bone that does not have a com- 

 plete representation in one of the four skulls. In number 1002 the lower ends are 

 still in contact with the pterygoid but the upper part is lost, it seems that the bone 

 articulated loosely by the intervention of cartilage much as in Sphenodon. The form 

 was that of a slender flattened pillar. 



The palatine : The palatines are slender plates closely attached to both the maxil- 

 laries and pterygoids. The attachment to the maxillary is very firm, a vertical 

 expansion of the bone is applied to the inner side of the alveolar edge and from this 

 springs the horizontal plate. The bone reaches from the posterior end of the maxil- 

 lary to a point opposite the canine tooth. The anterior end forms the posterior edge 

 of the posterior nares. 



The basi-sphenoid : The form of the basi-sphenoid is best shown in figures 4 and 

 5, PL V, the posterior end is swollen and articulates with the basi-occipital ; there is 

 evidence of the presence of considerable cartilage in this region during life. On the 

 lower surface there is a deep pit and near the anterior end two strong articular faces. 

 The anterior end terminates in a strong, median, vertical plate. 



The deep pit excavating the lower surface of the basisphenoid is in all probability 

 the lower opening of the eustachian tubes. In most reptilian forms the tubes pass 

 into the pharynx in the neigborhood of the basioccipital-basisphenoid suture and 

 anterior to the fenestra ovalis. In the crocodilia and the aglossal batrachians they 

 have a common opening into the mouth. In the present form the tubes probably 

 penetrated the large mass of cartilage covering the otic region and the posterior end of 

 the basisphenoid and found a common opening in the deep pit described. It is diffi- 

 cult to imagine the use of such an extensive cavity in the basisphenoid, but in the 

 Teleosauria an equally large cavity is found roofed over with bone. Anterior to this 

 pit two foramina penetrate the lower surface of the basisphenoid bone and on its 

 upper surface a large foramen appears just posterior to the origin of the parasphenoid 

 rostrum. Through the pair on the lower surface the internal carotid arteries enter 

 the bone and through the upper it gains access to the brain cavity by way of the 

 pituitary fossa. On either side of the single foramen a pair of small foramina carry 

 branches of the internal carotid. All of these foramina are very similar in position to 

 the same ones in Sphenodon. 



The two articular faces near the anterior end are the basipterygoid processes; 

 there are no corresponding articular faces on the pterygoid and it is evident from the 

 specimen 1002 where the bones of the palatal surface of the skull are little disturbed 



