PETERSON : DESCRIPTION OF NEW RODENTS 167 
dentition and the cranium furnish good specific characters, by which S. barbowri may 
be distinguished from the species first described herein. They are as follows : 
§ yi 
SUPERIOR DENTITION. 
The superior incisor is relatively shorter, more curved, and more abruptly 
sharpened, with the anterior face somewhat more rounded, than in S. fossor. ‘This 
tooth seems to agree more nearly with that indicated in S. pansus (Bull. Am. Mus. 
Nat. Hist., Vol. XX., 1904, p. 250), than with that of S. fossor. 
The cheek-teeth in S. barbowri have a relatively greater antero-posterior diameter 
in the skull than they have in S. fossor, but as in that species they are placed nearly 
parallel with the long axis of the cranium. The palate is also relatively broader 
in S. barbouri. Very little abrasion has taken place in p+, so that the grinding sur- 
face of the tooth has not attained its greatest diameter. The internal enamel invagi- 
nations of all the superior cheek-teeth continue to the alveolar border of the maxilla. 
This is not the case in S. fossor. Molar * is triangular in section. 
Wena Srqgieit, Jel ROWIOL, Ie, @)e Jel, ROWIUUL, Ii, 7A0), 
While the general outline of the skull of S. barbowri is similar to that of S. fossor, 
a closer study reveals characters, which, besides the smaller size, distinguish it from 
that of S. fossor. 
The distance from p+ to the incisor is relatively a little less in S. barbowri than 
in S. fossor. The palatine area of the premaxillaries, in S. barbowri, is very little 
higher than the palate; while this region in S. fossor is greatly arched (see PI. XVIT., 
fig. 1,and Pl. XVIIL., fig. 20). Theinterorbital space in S. barbowri is comparatively 
less constricted, and the temporal ridges are apparently less developed than in 8. 
fossor. ‘Chere may or may not have been a sagittal crest ; the parietals are crushed 
down in the type, so that a positive statement regarding this cannot be made, until 
the discovery of more material. The anterior part of the zygomatic arch is rela- 
tively less robust, and the tympanic bulla larger than in S. fossor. 
The contour of the skull of S. barbowrt is not unlike that of the skull figured and 
described as S. pansus (in Bull. Am. Mus. Nat. Hist., Vol. XX., 1904, p. 259). ‘The 
excavated basioccipitals, (distinctly a character of Custor), the shorter palate, and the 
more vertical and higher ascending ramus of the mandible in the specimen in the 
American Museum, however, are clearly characters that distinguish it from S. bar- 
bouri. The lattér species has the posterior nares back of m® ; the basioccipital is not 
excavated, and the ascending ramus of the mandible is at an angle similar to that 
in S. fossor. 
