936 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
Grizzly Buttes, Wyoming. Cited by Professor Cope as also occurring on the 
Upper Green River. Professor Cope considers this species as generically 
identical in dentition with Paramys, to which genus he refers it, as above 
cited. 
SCIURAVUS PARVIDENS Marsh. 
Sciuravus parvidens Marsu, Amer. Journ. Sci. and Arts, 3d ser. iv, 1872, 220, 
Half the size of Sczuravus undans, with the lower incisor more convex 
in front than in that species. Described from a “lower jaw containing the 
third molar, and part of an upper jaw with the penultimate molar, and sev- 
eral isolated teeth”. From Henry’s Fork and Grizzly Buttes, Wyoming. 
1SCIURAVUS —— Leidy. 
? Sciuravus —— Letpy, Extinct Vert. Fauna, 1873, 113, 335, pl. vi, fig. 30. 
Size of the last. Described and figured by Dr. Leidy (¢. c.) from part 
of a mandibular ramus, containing the third molar and the alveoli of the sec- 
ond and fourth molars, from Grizzly Buttes, Wyoming. Referred doubtfully 
to this genus by Dr. Leidy, it being considered by him as not referable to 
Paramys: 
GENus HELISCOMYS Cope. 
Heliscomys Corn, “‘Synop. New Vert Colorado, 1873, 3”; Ann. Rep. Geol. Surv. Terr. for 1873 (1874), 475. 
‘Tnferior molars four; the crowns supporting four isolated cones in 
pairs. This genus is only known from mandibular rami. These resemble in 
their dental structure some of the Muride, but the number of molars is 
more, as in Sciuride.” 
HELISCOMYS VETUS Cope. 
Heliscomys vetus Corn, “Synop. New Vert. Colorado, 1873,4”; Ann. Rep. Geol. Surv. Terr. for 1873 
(1874), 475. 
Smaller than Sciurus hudsonius. ‘The least mammal of the fauna to 
which it pertains.” ‘ First molar with only three cones; all the molars except 
the first with a broad continuous cingulum on the external side. Ramus 
rather stout; incisor-teeth very slender, elongate, slightly compressed, with 
parallel sides and convex anterior surface.” From the “Tertiary of Colorado”. 
GENUS MYSOPS Leidy. 
Mysops Leipy, Proc. Acad. Nat. Sci. Phila. 1871, 232; Ann. Rep. U.S. Geol. Sury. Terr. for 1871 (1872), 
357; Extinet Vert. Fauna, 1873, 111. 
“The jaw in its form, proportions, and construction, and the number of 
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