FOSSIL VERTEBRATES FROM SAN PEDRO VALLEY—GAZIN 507 
the anterior surface of P, is not grooved as in P. ? minor although 
this tooth is less worn than in the Benson jaw, and M; is not so re- 
duced as in P. % minor. There is no statement as to whether the 
teeth are rooted, but it is probable that they were not. Hence, it is 
possible that the Curtis ranch jaw, Amer. Mus. No. 27790, which 
Wood referred to P. ? minor may represent D. gidleyi or a closely 
related species. The two teeth in Amer. Mus. No. 27790 are well worn 
so that the absence of a groove on the anterior surface of P, is not 
significant. 
DIPODOMYS sp. 
The American Museum lower jaw, No. 27790 from Curtis ranch, 
which Wood (1935, pp. 155-156, fig. 73) referred to the Benson species, 
P. minor, includes P, and M,. These teeth are well worn, but M, is 
not rooted so that its representing the Benson species seems unlikely. 
Were the extent of individual variation in material of D. gidleyi 
known, it seems possible that this specimen might be shown to belong 
rather to D. gidleyi. The difference in pattern of P, in Amer. Mus. 
No. 27790 and Amer. Mus. No. 21848, the type of D. gidley?, as illus- 
trated can be attributed largely to difference in wear. 
NERTEROGEOMYS,” new genus 
Generic characters——Near Geomys, but P* exhibits enamel across 
the posterior wall and anterior column of P*, narrow, more as in 
Thomomys. Upper incisors grooved and anterior wall of lower 
molars without enamel as in Geomys. Mental foramen below anterior 
extremity of masseteric crest. Rostrum more depressed anteriorly 
with respect to plane of cheek teeth. 
Genotype-—Geomys persimilis Hay. 
NERTEROGEOMYS PERSIMILIS (Hay) 
A small pocket gopher is represented in the Curtis ranch collection 
by the rostral portion of a skull, No. 10492, the type of Nerterogeomys 
persimiis, having all the cheek teeth except P* and M® of the right 
side. To this was referred a right lower jaw, No. 10493, with the first 
three cheek teeth. A more fragmentary lower jaw with only P, was 
added to the collection in 1936. 
Nerterogeomys persimilis was originally described by Gidley as 
Geomys parvidens, but since this was preoccupied by G. parvidens 
Brown the name G. persimilis was proposed by Hay (1927, p. 186) for 
the Curtis ranch gopher. 
a2 vEpTEpos lower, below-+ Geomys, in allusion to its stratigraphic position. 
