506 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 92 
10490, of Citellus cochiset, and a left lower jaw, No. 10491, with the 
incisor and first two cheek teeth, was referred. A second lower jaw 
showing the alveoli for the cheek teeth and a portion of M, was added 
to the collection in 1936. 
The teeth in (@. cochisei differ from those of C. bensoni in being 
more compressed anteroposteriorly with more emphasis on the de- 
velopment of transverse crests such as in typical Citellus and Cyno- 
mys rather than as in Otospermophilus. The form is close in size 
to such species as Citellus columbianus of the Northwest and Citellus 
eversmannii of Siberia, larger than forms belonging to the subgenus 
Ictidomys, common in Cochise County, Ariz., today. 
The protocone in upper cheek teeth is not so compressed anteropos- 
teriorly as in recent material belonging in the subgenus C2tellus, but 
moderately so, such as in material ne Citellus mexicanus, alin 
the teeth are larger and relatively much wider than in this species. 
Moreover, as noted by Gidley, the valley between the protoloph and 
metaloph does not appear to extend so far lingually as in Recent 
Citellus, suggestive of Cynomys but with less development of the 
valley posterior to the metaloph; also, the teeth are more brachy- 
dont than in the Recent prairie dog. 
Comparison of (. cochiset with Citellus tuiitus Hay * from the 
early Pleistocene at Anita, Ariz. was not made by Gidley, but the 
differences between the forms were summarized by Howell *! in his 
revision of the North American ground squirrels: “Compared with 
tutus, it [C. cochisei| differs in having the protocone of the upper 
molars stouter and less hypsodont; the metaloph on M' and M? is sep- 
arated from the protocone by a wide sulcus; on M® the protoloph is 
likewise separated from the protocone by a wide sulcus; M* and M? 
are somewhat heavier than in tudtus but M? is relatively shorter.” The 
separation of the protocone from the protoloph or metaloph in the 
upper teeth of C. cochisei, indicated in the foregoing statement, ap- 
pears to be a condition ents due to wear. 
Cf. PEROGNATHUS sp. 
A lower jaw without cheek teeth, Amer, Mus. No. 27791, collected 
by Gidley at the Curtis ranch locality in 1924, was referred by Wood 
(1935 p. 107) to Perognathus. 
DIPODOMYS GIDLEYI Wood 
A species of Dipodomys in the Curtis ranch fauna was recognized 
by Wood (1935, pp. 156-159, fig. 74) on the basis of a right lower jaw, 
Amer. Mus. No. 21848, with cheek teeth P, to Mz preserved but in a 
fragmentary cond oe Among other characters it was noted that 
® O. P. Hay, Proc. U. 8. Nat. Mus., vol. 59, pp. 627-628, 1921. 
31 A. H. Howell, North Amer. Fauna 56, pp. 215-216, 1938. 
