MURID^— SIGMODONTES— ORYZOMYS. 



Ill 



(perhaps a Utile stretched), 3.75; tail to end of vertebrae, 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 mamma?, if existing, 

 have eluded our search, and were certainly not functionally developed in 

 this case. 



As already intimated, this single specimen is difJerenfiated from kuco- 

 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 leucogaster. But if any links exist, 

 they remain unknown. 



;'!'-■ 



SuBGENca ORYZOMYS, Baird. 



< Mu» Bp. Harlan, Am. Joiirn. Sci. 1837 . 



< ffeiperomi/o sp. Waonek, Siippl. Schreb. 1843. ' 

 X ^rrtoola ap. AUD. & Bach., Q. N. A. iii, 1853. 



= Oryzomyt, Baird, M. N. A. 1857, 458 ; typo, ilut paluiirti, Habl. 

 CouKS, 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 Zapodidm), 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 Fiber), with obliquely-set long toes; 

 densely pilous above, but soles perfectly naked, granular, with one long, nar- 

 row, ]K)slero-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 perfec^'y 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 v/here the 

 dermal scales as well as the vertebral annuli are visible. Fur glossy, l)ut 

 coarse from the number of bristly hairs. Whiskers sparse and short, exceed- 



