AHT. iS3. 



AN EXTINCT VAEANID LIZARD GILMORE. 



Basisphenoid. — The basisphenoid of Saniwa as in livinf^ lizards 

 generally sends downward two short processes or hypophyses with 

 flattened expanded ends that abut against the pterygoids, as in 

 Varanus (fig. 1). Between these processes at the middle it is 

 drawn out in front into a short truncated rostrum which articu- 

 lated with the presphenoid. The posterior margin is broadly notched 

 for the articulation of the basioccipital. The dorsal surface slopes 

 upward from the back toward the front, this inclination being con- 

 tinued on either side as divergent projecting processes which in 

 the articulated skull are lapped by a 

 slender projecting process of the 

 prootic. Between, and ventral to 

 these two processes the widened an- 

 terior end of the bone is deeply and 

 broadly scooped out, forming the sella 

 tertica, into which a pair of entoca- 

 rotid canals open. On the lateral pos- 

 terior surface is a foramen that in 

 Va?'amis leads diagonally through the 

 wall of bone into the median excava- 

 tion described above. This bone in 

 size and shape is remarkably similar 

 to the basisphenoid of Varanus sal- 

 vatoT (Cat. No. 29408 U.S.N.M.). 



Exoecipital and opistliotic. — Both 

 exoccipital bones are present, the left 

 having the prootic of that side at- 

 tached to it. The exoccipital con- 

 tributes to the basal as well as form- 

 ing all of the side boundary of the 

 foramen magnum. The basal portion 

 extends backward and forms the lat- 

 eral portion of the occipital condyle. 

 Articulated it would extend outward 

 and backward as a flattened paraoccipital process having a vertically 

 expanded, truncated end, which probably articulated with the supra- 

 temporal and quadrate as in Varanus. A foramen leads diagonally 

 through this bone into the brain cavity, having its external exit ven- 

 tral to the lower border of the paraoccipital process. Beneath and 

 forward of this vagal foramen, a small, thin, winglike horizontal 

 plate is developed which joins the lateral border of the basioccipital. 

 In the comparatively limited development of this platelike process. 

 with a decided notch between it and its junction with the paraoc- 

 cipital process, it resembles the Iguana much more closely than Vara- 

 nus, where this process extends outward on the lower side of the para- 



FiG. 2. — Ventral view of sklll 

 BONES OF Saniwa ensidens Leidv. 

 Cat. No. 2185. U.S.N.M., type. 

 All natural size. A, Right 



I'TERYGOID. Ect, PROCESS AUTICn- 

 LATING WITH THE ECTOPTERYGOID ; 

 P, PROCESS THAT UNITES WITH THE 



PALATINE. B, Basisphenoid ; hyp, 

 hypophyses; p,s, presphenoid, 

 WHICH is missing. C, Basioc 

 cipital ; oc, occipital condyle re 

 stored. D, Right ectopterygoid, 

 dorsal view ; rnx, a.nterior end 

 that meets the maxillary ; pt, 



POSTERIOR bifurcated END THAT 

 MEETS THE OUTER BRANCH OF THE 

 PTERYGOID. 



