0. C. Marsh—New Tertiary Mammals. 219 
nim. 
Transverse diameter of UMOIROT oss week che cee ee 4° 
The specimens above described were found by Mr. G. G. 
Lobdell, Jr., and Mr. G. M. easbey, in the lower Tertiary de- 
posits of Grizzly Buttes and Henry’s Fork, Wyoming. 
Tillomys senex, gen. et sp. Nov. 
A small rodent, about the size of a rat, is represented in our 
Wyoming collections by a fragment of a lower jaw with the 
second molar in place, and apparently by some other uncharac- 
teristic remains. The crown of this molar is somewhat worn, 
Measurements. 
Space occupied by four lower molars,.....-..+++++ee+ee+ ery 
Antero-posterior diameter of second lower molar,........ 2° 
ET OrOO CRM Ot tdi end si dagen intmee seen canes 1°8 
Depth of jaw below second WIDMER oud conc. Sxeen cee 5° 
The known remains of this species were found, in September 
last, by the writer, near Henry’s Fork. 
Tillomys parvus, sp. nov. 
of the last lower molar, The species was but little larger than 
& mouse, 
Measurements. 
Kength of lower molar seTrieS,.. «+0. se+ esse ceeserscvese vs 
tero-posterior diameter of second lower molar,........ s 
Transverse diametar, .. .ossa0ssescnenpeerh ieee? 
Pace between incisor and first lower molar,.....-......-3" 
This specimen was found by Mr. O. Harger, at Grizzly Buttes, 
Wy oming, in September last. 
Taxymys lucaris, gen. et sp. Nov. 
The existence of another small rodent, evidently belonging to 
the Sciuridee, is clearly proved by a fragment of an upper jaw, 
