FOSSIL VERTEBRATES FROM SAN PEDRO VALLEY—GAZIN 487 
condition indicated by the alveolus of the otherwise hypsodont M, in 
the type of P. ? minor. 
The evidence of small rootlets on M, of P. ? minor might suggest 
that this form should be referred to Cupidinimus,; however, teeth in 
P. ? minor are markedly hypsodont, and correspondence to the mod- 
ern genus, Dipodomys, in this and other characters seems much closer 
than to Cupidinimus, as characterized by the genotype, C. nebraskensis. 
Upper teeth, Amer. Mus. No. 21835, from the Benson locality, which 
Wood (1935, pp. 146-148) referred to Cupidinimus magnus, include 
grooved upper incisors as in Dipodomys, but the first two cheek teeth 
preserved are stated to be rooted. These are markedly hypsodont 
though much worn. On the basis of Wood’s description it seems prob- 
able that these are upper teeth of P. ? minor. 
NERTEROGEOMYS 7? MINOR (Gidley) 
The Benson species described by Gidley as Geomys minor is believed 
to represent the new genus Nerterogeomys, described in the portion of 
this paper concerned with the Curtis ranch fauna, and having for a 
type the species Geomys persimilis Hay. 
The type of Nerterogeomys ? minor is a right mandibular ramus, 
No. 10494, with the incisor and P, to M,. To this was referred an 
upper incisor, No. 10534, and a few isolated cheek teeth. Unfortu- 
nately, the illustration given by Gidley for the upper incisor was inter- 
changed with that for a Cratogeomys bensoni incisor, so that the small 
incisor shown in his plate 34, figure 11, is actually that belonging to 
Nerterogeomys ? minor and not Cratogeomys bensoni. 
The lower jaw of V. ? minor is a little smaller than that of Geomys 
texensis and with somewhat narrower teeth, although the enamel on 
these is arranged as in the living species. The fossa for the temporal 
muscle on the lingual side of the ascending ramus and posterolateral 
to the molars is not so deep and does not extend so far forward as in 
Recent Geomys but is apparently better developed than in Thomomys. 
Also, the masseteric crest extends a little farther forward with respect 
to the cheek teeth, with the mental foramen below its anterior extremity 
as in Nerterogeomys persimilis, lower and more posteriorly placed 
than in Geomys texensis. 
The upper incisor referred to this species conforms in size and is 
of the bisulcate type characteristic of Geomys and Nerterogeomys. 
CRATOGEOMYS BENSONI Gidley 
The type of Cratogeomys bensoni is a left lower jaw, No. 10495, 
carrying all the cheek teeth but lacking the incisor. To this species 
were referred four additional lower jaws having various teeth pre- 
served and an isolated upper and lower incisor. As noted in the 
above description of Nerterogeomys ? minor, the figure of the upper 
