452 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 5° 



Symphysis long, occupying about two-thirds the length of the jaw. Outer 

 side of lower jaw with long vascular impressions, which often unite to form a 

 groove, which is broad and shallow at first and afterward narrow and deep. 

 Angle of the symphysis rounded. The lower borders of the rami concave, 

 the upper bent inward, so that, seen i. m above, the rami, with the angle of 

 the symphysis, assume an elongated oval form. Alveoli numerous, reaching 

 up on the rami. Teeth small ; those on the rami short cone-shaped, with the 

 crown bent backward and swollen above the base. 



Pretuaxillae approximated, anchylosed together in age, depressed in the 

 nasal region, with many grooves in the broader part which converge an- 

 teriorly. Nasals small. Interparietal enclosed between the two frontals and 

 the occipital. Frontals mostly free, covered by the maxilke only on the sides. 1 



The skull of crassangulum presents the majority of these char- 

 acters, and especially those of the lower jaw, on the conformation of 

 which, according to Dr. Abel, the chief reliance is to be placed. As 

 nearly all of the brain-case and adjoining parts are lacking, the agree- 

 ment, as regards the form of the frontals, nasals, etc., cannot be 

 determined. 



Schisodelphis sulcatus is peculiar as regards the form of the brain- 

 case. The supra occipital is very low and the frontals occupy a very 

 large area on the vertex. As a result, the cranium is depressed and 

 somewhat rectangular, and the temporal fossae are irregularly pent- 

 angular. The palate is deeply grooved and its surface more or less 

 rounded. The teeth are comparatively few in number and widely 

 spaced, but the two rows are closely approximated anteriorly, at 

 least in the mandible. 



In the shape of the palate, the greater number of teeth, and the 

 greater relative distances between the rows, Schisodelphis crassan- 

 gulum differs from sulcatus. It seems best at present, however, to 

 regard these differences as specific rather than generic. 



Mr. Case has described the type specimen of crassangulum quite 

 in detail. The following notes relate chiefly to characters which are 

 not mentioned by him, or to such as seem to me worthy of a more 

 extended description : 



At the middle point of the rostrum a cross-section of the pre- 

 maxillae forms nearly the quadrant of a circle, the height and breadth 

 being about equal. As they extend forward they become gradually 

 more depressed, while posteriorly they become higher, until they 

 reach a point about opposite the posterior end of the tooth-row, be- 

 yond which they become rapidly lower again and also broader. This 

 broad portion is nearly flat. It is succeeded further back by a second 

 broad, flattened area, which is separated from the first by a distinct 



1 Denkschr. k. Akad. Wiss. Wien, Math. -Nat. -Wiss. Classe, 68, 1900, p. 849. 



