.Hi; MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



Genus PSBUDOTOMUS Cope. 



Pteudotomut Cope, Proo. Amer. Phil. Boo. 187a, 467; U. S. Geol. Surv. Terr. 6th Ann. Rep. (for 1872), 

 l-?:;, 610. 



Skull depressed; zygomata considerably expanded; muzzle broad, but little ele- 

 vated, with the nasal meatus between the alveoli of the upper incisors; frontals very 

 short, the superciliary margin and orbits small, and without postorbital processes; 

 temporal fossa- large, converging posteriorly, aud greatly contracting the brain case 

 behind the orbits; infraorbital foramen rather small, circular, and placed low dowu 

 near the alveolar border; upper incisors relatively small, in form much as in Arctomys, 

 but more widely separated; molars probably f. 



This genus was first referred by its describer to the order Edentata, but later was 

 considered as "allied to, if not actually a member of, the Schtridw". The breadth and 

 depression of the skull are said to remind one of Arctomys, from which, however, it 

 differs in the contraction of the skull between the orbits, in this respect more resembling 

 Fiber. It seems also in this and in other respects to strongly recall Ischyromys. The 

 lateral separation of the iucisors, both superior aud inferior, is referred to as a marked 

 peculiarity. Known from a single imperfect skull aud one or two mandibular fragments 

 from the Bad Lands of Cottonwood Creek. 



PSE1 DOTOMDS HIANS Cope. 



I'm udotomus Mans Cope, Proc. Auier. Phil. Soc. 1S72, 467 ; U. S. Geol. Surv. Terr. Oth Ann. Rep. (for 1872), 

 1873, 611. 



The siugle imperfect skull from which the present species is known is said to indi- 

 cate an animal of "about the size of an Agouti". From the Fort Bridger Eocene. 



MYOMORPHA. 

 MURIDJE. 



Genus EDMYS Leidy. 



Eumya Leidy, Proc. Acad. Nat. Sci. Phila. 1856, 90. 



EUMYS ELEGANS Leidy. 



Eumya elegant Leidy, Proc. Acad. Nat. Sci. Phila. 1856, 90; 1857, 89; Journ. Acad. Nat. Sci. 2d ser. vii, 

 1869, 342, 407, pi. xxvi, tigs. 12, 13.— Cope, Rep. U. S. Geol. aud Geog. Surv. Terr, for 1873, 

 1874,474. 



The genus aud species were described by Dr. Leidy from a specimen discovered by 

 Dr. Haydeu in the Bad Lauds of Bear Creek, "consisting of a portion of the left side 

 of a lower jaw". This jaw-fragment is said to indicate "an animal approaching in 

 size the Brown Rat (Mus <l<eii>nani<s) , \ and to agree in form and constitution with the 

 corresponding portion of the jaw of that animal. 



I.i MYS LOXODON Cope. 



ffeeperomys loxodon Cope, Proc. Acad. Nat. Sci. Phila. 1874, 150. 



Eumys loxodon Cope, Auu. Rep. Chf. Lugineers, 1874, 605; ib. App. LL, 1. 



Based on an entire mandibular ramus, with all the teeth preserved, from the Sauta 

 Fe marls. Similar to the E. elegans of Leidy. 



M,iim\i\ MAGISTER Baird. See anted., p. 29 



