312 CRATOGEOMYS, 
to occiput near median line; breadth of cranium posteriorly less 
than zygomatic breadth; zygomata broad and heavy. 
Fig. 57. CRATOGEOMYS CASTANOPS. 
No. 4 Field Columbian Mus. Coll. Nat. size. 
KEY LO SPECIES AND SUBS PECGIES: 
*A. Basioccipital truncate, wedge-shaped. (Sides 
approximating anteriorly.) 
a. Sagittal crest well developed. 
a.’ Lower incisor strongly beveled on outer PAGI 
side. . Fay ei aes .C. merriamt 313 
b.? Lower incisor not beveled on outer side. 
ae Top of skull strongly convex 1n profile KE: fulvescens 310 
b.”” Top of skull nearly flat in profile. 
a.’”’ Nasals normal, rather long and nar- 
row rt eee ee .C. perotensis 313 
b.’’’ Nasals short, narrow posteriorly, 
broad anteriorly . ...C. estor Vame 
* Merr. Mon. Geomyide, p. 151 
