PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 60. 



Fig. ^5.- — Right exoc- 



CIPITAL OF SaNIWA 

 ENSIDEN.S LEIDY. 



Cat. No. 2185, 

 U.S.N.M.,TYPE. Na- 

 tural SIZE. Pos- 

 terior VIEW. 



occipital process for fully one-half its total leng-th, while in Saniwa 

 its extent Avould be less than one-fourth the total leng^th. On the an- 

 terior side of the paraoccipital process, a sharp median longitudinal 

 ridge divides the lower nonarticular from the upper articular surface 

 with which it unites with the posterior branch of the prootic by 

 squamous suture. On tlic inner anterior end a deep pit, a part of 

 the auditory capsule, extends down into this bone. Immediately 

 Avithin the foramen magnum the exoccipital is perforated by a small 

 foramen for the passage of the hypoglossal nerve. 

 Avhich makes its exit beneath the base of the lateral 

 paraoccipital process. 



In front of this foramen is a slitlike aperture, the 

 internal auditory meatus, through which the audi- 

 tory nerve leaA^es the cranial cavity and enters the 

 external ear. In the crocodile the thin bone above 

 and in front of this slitlike opening is the opis- 

 thotic, and from the close resemblance of this por- 

 tion of the Saniwa brain case to that of the crocodile leads me to 

 believe that the thin bone above the slit, forming a wall betAveen the 

 auditory capsule and the brain cavity, is the opisthotic, which, as in 

 many other reptiles, has become united with the exoccipital early in 

 life. Attached to the right exoccipital is a fragment of the rodlike 

 columnella auditoris. 



Supraocclpital. — The supraoccipital has a more pronounced 

 median keel than in Varanus^ and in this respect is intermediate be- 

 tween Iguana and Varanus. As in the latter genus, it forms the 

 superior boundai'y of the foramen magnum. The 

 upper end terminates obtusely, but is not so broad 

 as in Varanus. Latterly it joins the exoccipitals ; 

 anteriorly the prootics and opisthotics, superiorly 

 the parietal but by cartilagenous attachment only. 

 Epipterygoid. — The complete left epipterygoid 

 and a portion of the right are present. It is a 

 rounded bar with slight, but about equally ex- 

 panded ends. The loAver end is cut off obliquely, 

 the upper is flattened on the inner side, Avhere it 

 laps against the forward extremity of the prootic 

 a total length of 16 mm. 



Pterygoid. — The right pterygoid is present in its entirety, the left 

 nearly as perfect. The latter Avas found in the matrix but little sepa- 

 rated from its proper articulation Avith the ectopterygoid (see pi. 1) 

 and palatine bones. The pterygoid in Saniwa is a long, slender, 

 slightly curved bone, having a bifurcated anterior end and a flat- 

 tened tapering posterior extremity Avhich laps the inner distal side 

 of the quadrate (see A, fig. 2). The slender rodlike posterior por- 



FiG. 4. — Right epi- 

 pterygoid OF Sa- 

 niwa ENSIDENS 

 Leidy. Type. Cat. 

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

 Natural size. 



rOSTERIOK VIEW. 



This bone has 



