66 The Alligator and Its Allies 



the pterygoids behind to the maxillae in front. 

 They are united with each other by a straight 

 median suture and form a considerable part of the 

 floor as well as a part of the side walls and roof of 

 the nasal passage. They form most of the median 

 boundaries of the posterior palatine vacuities (pv) . 

 Dorsally they articulate with the pterygoids, pre- 

 frontals, and vomers. 



The pterygoids (10) are the very irregular bones 

 that project ventrad and caudad from beneath the 

 orbits. Their suture is continuous, caudad, with 

 that between the palatines and at the posterior end 

 of this suture is the posterior opening of the nasal 

 chamber, the posterior nares (pn). This opening 

 is divided by a vertical, longitudinal, bony septum, 

 and the part of the chamber into which it immedi- 

 ately opens, which lies in the pterygoids, is divided 

 by a number of transverse, vertical septa. Poste- 

 rior and dorsal to the posterior nares the pterygoids 

 are fused. Anteriorly the pterygoids articulate 

 with the palatines; dorsally with the quadrates, 

 basisphenoid, alisphenoids, and prefrontals, and 

 dorso-laterally with the transpalatines. The lat- 

 eral vertical border of the pterygoid is roughened 

 and is, according to Reynolds, covered, during life, 

 with a pad of cartilage against which the medial 

 side of the mandible plays. 



The transpalatine (n) is a T-shaped bone articu- 

 lating ventrally with the pterygoid and dorsally 

 with the maxilla, the jugal, and the postfrontal. 



