SCIURIDH—EXTINCT SPECIES. 939 
slender, with the tubercle at the anterior margin of the masseteric fossa under 
the centre of the second molar. The crown of the tooth has an anterior 
transverse crest and a pair of posterior tubercles. From the lower Tertiary 
deposits, Henry’s Fork, Wyoming. 
TILLOMYS PARVUS Marsh. 
Tillomys parvus MarsH, Amer. Journ. Sci. and Arts, 3d ser. iv, 1872, 219. 
Considerably smaller than the preceding. Length of lower molar series 
7.1™™. Described from a similar imperfect lower-jaw fragment containing 
the second molar, from Grizzly Buttes, Wyoming. 
_ 
