MURIDA—SIGMODONTES—ORYZOMYS. nti 
(perhaps a “itéle stretched), 3.75; tail to end of vertebra, 1.90; to end of 
hairs, 2.00; fore foot, 0.40; hind foot, 0.80; ear 0.70 high, 0.40 wide. 
Camp Grant, Arizona. The specimen is a female, apparently having recently 
bred, showing four well-developed inguinal teats; pectoral mamme, if existing, 
have eluded our search, and were certainly not functionally developed in 
this case. 
As already intimated, this single specimen is differentiated from Jeuco- 
gaster according to extensively applicable laws of geographical variation; for 
which reason we suspect that intermediate examples will eventually be found, 
showing it to be merely an offset from /eucogaster. But if any links exist, 
they remain unknown. 
Suseenus ORYZOMYS, Baird. 
<_ Mus sp. HARLAN, Am. Journ. Sci. 1837 
< Hesperomys sp. WAGNER, Suppl. Schreb. 1843. = 
x Arvicola sp. AuD. & Bacu., Q. N. A. iii, 1853. 
= Oryzomys, BatrD, M. N. A. 1857, 458; type, Mus palustris, Har. 
Cougs, Proc. Acad. Nat. Sci. Phila. 1874, 183. 
CHARS. 
Superior margin of orbit with a prominent sharp edge or bead. 
Anteorbital foramen nearly circular above (somewhat as in Zapodide), con- 
tinued below as a slit much narrower than in Hesperomys proper. Maxillary 
plate forming outer wall of the foramen not produced anteriorly into a pointed 
process (cf. Sigmodon). Posterior border of palate produced behind last 
molars, a deep pit intervening on either side; post-palatal notch narrow, with 
parallel sides, and nearly straight, transverse, anterior border. Hind legs short, 
but feet very long and large (much as in Fvber), with obliquely-set long toes ; 
densely pilous above, but soles perfectly naked, granular, with one long, nar- 
row, postero-internal tubercle (as in Mus) and five small ones. Lateral toes 
very unequal in length, the fifth reaching to the penultimate joint of the fourth 
(cf. Sigmodon); all the toes have a slight but evident basal webbing. Fore 
feet small, not half as long as the hinder, pilous above ; palms perfectly naked. 
Ears small, little overtopping the fur, hirsute both sides, with a fluffy tuft on 
the concavity. Nasal pads more noticeable than in other sections. Tail 
long, about equaling head and body, scant-haired, especially above where the 
dermal scales as well as the vertebral annuli are visible. Fur glossy, but 
coarse from the number of bristly hairs. Whiskers sparse and short, exceed- 
