O.'JG 



MONOGkAl'lIS OF NOrwTU AM13UICAN RODENTIA, 



m' h 



(jlrizzly Hiittrs, Wyoming. Citctl by Professor Cope as also occurring on the 



U|i|)iT (irfi-n K'ivcr. Professor Cope considers this species as giMierirally 



idenlical in denliiiou with Pnrani>/s, \o which genus he refers it, as above 



cited. 



SCIURAVUS TARVIDENS Marsh. 



Stiiirariit pani<U-n$ Mafisii, Amur. Joiirn. Sci, anil Arts, 3(1 ser. iv, 1373, S'20 



Half the size of Sciuravus und<ivs, witli the lower incisor more coriv(;x 

 in fiont tiian in tiiat species. Described from a "lower jaw containing the 

 thini 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. 



f Sdvrariid Lkidv, Extinct Vort. Fauna, 1673, 113, 335, pi. vi, flg. 30. 



Size of the last. Described and figured by Dr. Leidy (/. c.) from part 

 of a maudibidar ramus, containing the third molar and the alveoli of the sec- 

 oiul and fourth molars, from Grizzly Buttes, Wyoming. Referred doul)tfully 

 to this genus by Dr. Leidy, it being considered by him as not referable to 

 Paramt/s. 



Genus IIELISCOMYS Cope. 



ncUtoomyn CoPE, " Synop. Now Vert Colorado, 1S73, 3 " ; Ann. Rep. 0«ol. Burv. Terr, for 1973 (1874), 475. 



"Liferior molars four; the crowns supporting four isolated cones in 

 pairs. Tliis genus is only known from mandibular rami. These resemble in 

 their dental structure some of the Murida, but the number uf molars is 

 more, as in Sciuridce." 



IIELISCOMYS VETUS Cope. 



UeliKomyi rtlia CoPK, "Synop. Kow Vert. Colorado, 1S73,4"; Ann. Bcp. OeoL 8unr. Terr, for 1873 



(1-^7 1), ITS. 



Smaller than Scinrus hudsonius. " The least mammal of tlie fauna to 

 which it pertains." "First molar with only three cones ; all the molars except 

 the first with a broad continuous cingulum on the ex ernal side. Ramus 

 rather stout; incisor-teeth very slender, elongate, slightly comrnct-.^fi, wHi; 

 parallel sides and convex anterior surface." From the "Tertiary of Colorado". 



Genus MYSOPS Leidy. 



Ujimpt Lkibv, Proc. Acad. Nat. Sci. Pliilii. 1871, 8.13; Ann. Bep. U. 8. Oeol. Burr. Terr, for 1871 (1S72), 

 3.W; Kxlinct Vert. l''auua, 1H7.'!, 111. 



"The jaw in its form, proportions, and const ructiuii, and the number of 



