492 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 92 
Order LAGOMORPHA 
HYPOLAGUS sp. 
The lagomorph material, No. 10529, from the Benson locality, which 
Gidley referred to Species No. 2, clearly represents Hypolagus. Gid- 
ley’s description as well as an examination of the material shows 
this to be the case; however, the specimen is too fragmentary to war- 
rant detailed comparisons with other species of the genus. Never- 
theless, P; in this material is seen to be a little larger than this tooth 
in Hypolagus browni from Anita, Ariz. 
Certain of the upper teeth included in No. 10535, which Gidley re- 
ferred to as cf. Lepus sp. from the Benson locality, appear to represent 
Hypolagus, although an incomplete P; under this number may repre- 
sent Sylvilagus % bensonensis. Probably more than one individual 
is included in the material. 
SYLVILAGUS ? BENSONENSIS, new species 
FIGURE 39 
Type.—Leit ramus of mandible, U.S.N.M. No. 16595, including 
P, to M, inclusive. 
Locality —About 2 miles south of Benson, Ariz., in exposures on 
the west side of the valley. 
Horizon.—Possibly Benson (Late Pliocene) in age, though not from 
quarry worked by Gidley and Bryan. 
Specific characters.—Size near Sylvilagus floridanus holzneri now 
living in Arizona. Jaw relatively robust. P,; without reentrant from 
anterior wall but anterior external rentrant deep and complex. 
Description.—The fossil jaw is near 
specimens of Sylvilagus floridanus 
5 holzneri or S. auduboni cedrophilus 
ate in size, but appears relatively ro- 
Lie bust, particularly in depth anterior 
Frcure 39.—Sylvilagus? bensonensis, to the cheek teeth. The most notice- 
new species: Left lower cheek teeth, able differences, however, are to be 
P; to My (U.S.N.M. No. 16595), : 
type specimen, occlusal view of seen in the enamel pattern of Be 
enamel pattern. Approximately x The posterior portion of all the folds 
6. Benson upper Pliocene, Arizona. 
from the buccal surfaces of the cheek 
teeth are markedly crenulated, but in P,; the anterior reentrant 
from the outer surface is much more deeply impressed and more 
highly crenulated than in any of the modern Sylvilagus material 
which I have examined. Moreover, this tooth lacks the reentrant 
from the anterior wall seen in Sylvilagus, Lepus, and certain other 
genera. Some forms of Sylvilagus, etc., have two reentrants on the 
anterior wall, whereas in Romerolagus and Brachylagus, forms other- 
wise distinct from S. ? bensonensis, P,; shows little or no fold in this 
