J46 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
GENUS PSEUDOTOMUS Cope. 
Pseudotomus Corr, Proc. Amer. Phil. Soc. 1872, 467; U. S. Geol. Surv. Terr. 6th Ann. Rep. (for 1872), 
1873, 610. 
Skull depressed; zygomata considerably expanded; muzzle broad, but litéle 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 fosse large, converging posteriorly, and greatly contracting the brain case 
behind the orbits; infraorbital foramen rather small, circular, and placed low down 
near the alveolar border; upper incisors relatively small, in form much as in Arctomys, 
but more widely separated; molars probably 3. 
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 Sciuride”. 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 incisors, both superior and inferior, is referred to as a marked 
peculiarity. Known from a single imperfect skull and one or two mandibular fragments 
from the Bad Lands of Cottonwood Creek. 
PSEUDOTOMUS HIANS Cope. 
Pseudotomus hians Core, Proc. Amer. Phil. Soc. 1872, 467; U. S. Geol. Surv. Terr. 6th Ann. Rep. (for 1872), 
1873, 611. 
The single 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. 
MURIDZ. 
Genus EUMYS Leidy. 
Eumys Lewy, Proc. Acad. Nat. Sci. Phila. 1856, 90. 
EUMYS ELEGANS Leidy. 
ELumys elegans Leroy, Proc. Acad. Nat. Sci. Phila. 1856, 90; 1857, 89; Journ: Acad. Nat. Sci. 2d ser. vii, 
1869, 342, 407, pl. xxvi, figs. 12, 13.—Core, Rep. U. 8. Geol. and Geog. Sury. Terr. for 1873, 
1874, 474. 
The genus and species were described by Dr. Leidy from a specimen discovered by 
Dr. Hayden in the Bad Lands 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 (J/us decumanus)”, and to agree in form and constitution with the 
corresponding portion of the jaw of that animal. 
EUMYS LOXODON Cope. 
Hesperomys loxodon Cop®, Proc. Acad. Nat. Sci. Phila. 1874, 150. 
Eumys loxodon Corr, Ann. Rep. Chf. Engineers, 1874, 605; ib. App. LL, 1. 
Based on an entire mandibular ramus, with all the teeth preserved, from the Santa 
Té marls. Similar to the L. elegans of Leidy. 
NEOTOMA MAGISTER Baird. See anted, p. 29 
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