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;SPE ClESFAND SUBSPRE GIES; 
* A. Basioccipital truncate, wedge-shaped. (Sides 
approximating anteriorly.) 
a. Sagittal crest well developed. 
a.’ Lower incisor strongly beveled on outer PAGE 
SIGE A 0 Se Ree .eeeepere hyer es .C. merriamt 313 
b.’ Lower incisor not beveled on outer side. 
a.’’ Top of skull strongly convex in profile. ..C. fulvescens 316 
b.” Top of skull nearly flat in profile. 
a.’’’ Nasals normal, rather long and nar- 
OW .C. perotensis 313 
b.’’” Nasals short, narrow posteriorly, 
broad anteriorly GCG. estor 278 
* Merr. Mon. Geomyide, p. 151 
