936 MONOGRAPHS OF NORTB AMERICAN RODENTIA. 



( i rizzly Buttes, Wyoming. Cited by Professor Cope as also occurring on the 

 Upper Green River. Professor Cope considers this species as genetically 

 identical in dentition with Paramys, to which genus he refers it, as above 



cited. 



SCIURAVUS PARVIDENS Marsh. 



Sciuravus parvidens Marsh, Amor. Journ. Sci. and Arts, 3d ser. iv, 1872, 220, 



Half the size of Sciuravus u ndans, with the lower incisor more convex 

 in front titan 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. 



\ SCIURAVUS Leidy. 



? Sciuravus Leidy, Extinct Vert. Fauna, 1873, 113, 335, pi. vi, fig. 30. 



Size of the last. Described and figured by Dr. Leidy (7. 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 IIEL1SC0MYS Cope. 



Beliswmys Cope, " Synop. New Vert Colorado, 1873,3"; Ann. Eep. Geol. Surv. Terr, for 1873 (1874), 475. 



"Inferior 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 Muridce, but the number of molars is 

 more, as in Sciuridce." 



HELISCOMYS VETUS Cope. 



Heliscomys veins CorE, "Synop. Now Vert. Colorado, 1873,4"; Ann. Rep. Ceol. 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. 



. Sci. Phila. 1871, 332; Ann. Rep. U. S. 

 Fauna, 1-7:!, 111. 



The jaw in its form, proportions, and construction, and the number of 



Mysopt Leidy, Proc. Acad. Nat. Sci. Phila. 1871, 232; Ann. Rep. U. S. Geol. Surv. Terr, for 1871 (1872), 

 357; Extinct Vort. Fauna, 1873,111. 



