4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.67 



supraorbital process. The maxilla sheathes the internal face of this 

 ''upended" process and its outer margin follows the crest of the 

 latter. Behind this process, the maxilla expands horizontally and is 

 applied to the platelike lateral extension of the frontal which in turn 

 contributes the roof for the temporal fossa. The temporal fossae 

 are not visible from a dorsal view and the external margin of the 

 maxilla curves backward from the postorbital projection to the trans- 

 verse crest of the supraoccipital. At the level of the nasals the 

 whole maxilla curves strongly upward to the transverse crest of 

 the supraoccipital. The dorsal margin of the supraoccipital and the 

 posterior borders of the maxillae together comprise the transverse 

 lambdoid crest. Behind the temporal fossae the lateral margins of 

 the supraoccipital are applied to the posterior borders of the parietals 

 and these combined bones form the thin posteriorly directed lambdoid 

 crest which follows the curvature of the inner and lower margins of 

 each temporal fossa. 



As in the other skull (Cat. No. 10485, U.S.N.M.) the raised con- 

 vex portions of the premaxillae are widest in front of the premaxillary 

 foramina and taper rapidly posterior to the latter, disappearing in 

 front of the nasal passages. Both premaxillary foramina are com- 

 pressed dorso-ventrally and of large size; the greatest diameter of 

 the right foramen is 10.5 mm. The right foramen is situated 42 

 mm. in front of the level of the antorbital notches and the left 37 

 mm. From each foramen a broad groove passes forward along the 

 internal border of the raised convex outer portion of the premaxilla. 

 On the other skull a groove also extends backward from each fora- 

 men in an oblique direction across the premaxilla and terminates 

 near the level of the posterior margin of the "upended" crestlike 

 portion of the supraorbital process. On the second skull the orifice 

 of the premaxillary foramen looks inward and forward. This change 

 in direction of the foramen leaves the posterior margin elevated above 

 the level of the anterior groove and shuts off the posterior groove at 

 the source. The premaxillae are separated by an interval of 17 mm. 

 above the porous pluglike portion of the presphenoid. The pre- 

 sphenoid does not rise to the level of the premaxillae, as in the first 

 skull. Behind the level of the antorbital notches the dorsal aspect 

 of the ascending process of each premaxilla is convexo-concave, the 

 surface sloping from the external to the internal margin. Between 

 the nasal passages and the antorbital notches the internal border of 

 each premaxilla is deflected obliquely downward. The peculiarities 

 of the premaxillae are essentially the same on both skulls. At the 

 level of the anterior margins of the nasals the premaxillae are quite 

 deep, and at the postero-external angle the dorsal surface is raised 

 at least 20 mm. above the horizontally expanded plate of the max- 

 illa. The posterior end of each premaxilla is obliquely truncated, 



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