484 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 92 
lished, but these suggest the possibility of a stage not greatly different 
from that at Curtis Ranch. 
The fauna from near Grand View, Idaho, studied in part by Wilson 
and the writer, has not been completely recorded. This fauna might 
be of a relatively early Pleistocene stage but appears to be close to 
that of Hagerman and may well be a slightly later stage of Blancan 
or upper Pliocene. The rodents, lagomorphs, and carnivores are more 
closely related to those of Hagerman than the Curtis ranch forms are 
to those of Benson. The horse from Grand View is regarded by J. R. 
Schultz as Plesippus idahoensis, a much larger form than P. sho- 
shonensis and nearer true Hquus. 
Comparison of the San Pedro Valley faunas with that of Hager- 
man brings out a number of interesting facts pertaining to the 
environments of each. Although the Benson fauna is evidently close 
in age to that of Hagerman, the two San Pedro Valley faunas 
are more strikingly alike in the type of environment indicated, 
and quite unlike the Hagerman assemblage. The rodent group is 
most significant as indicative of habitat, and in both San Pedro Val- 
ley faunas has a large percentage of the more brachydont cricetine 
forms. These genera, though nearly all wide ranging in the modern 
fauna, are abundantly represented in tropical to arid southern 
regions. The heteromyids are related to forms of common occur- 
rence in the desert regions of the Southwest. However, a watered area 
is in no way precluded, and is evident from the avifauna and sug- 
gested by certain of the rodents. Standing water or streams of a 
saline nature would discourage the more water-loving types of mam- 
mals, though ducks and the like might be plentifully represented. 
In contrast to this the Hagerman fauna shows a preponderance of 
forms associated with fresh water. These include fishes, frogs, aqua- 
tic birds, otter, beaver, and muskratlike forms. The birds are all 
aquatic, otters are the most common of the Carnivora, and the rodents 
are predominantly beaver or of the hypsodont, microtine type of 
cricetids. 
SYSTEMATIC DESCRIPTION OF THE BENSON MAMMALIAN FAUNA 
Order CARNIVORA 
Canid sp. 
A relatively large canid is indicated by the presence in the Benson 
collection of an incomplete third metatarsal, No. 12859. The bone is 
proportioned about as in material of Aenocyon dirus from Rancho 
La Brea but is somewhat larger. In robustness it compares favor- 
ably with a third metatarsal from the Pliocene at Long Island, Kans., 
referred to Aelurodon, but though incomplete distally, the Benson 
specimen appears to have been longer. 
