181 PROCEEDINGS OF THE ACADEMY OF 



9- Hesperomys (Oryzomys) palustris, (Harlan) Baird. 



Syn. Mm paluHvis Harl., Am. Journ. ScL, xxxi. 1837, 38G (New Jersey). 



Hesperomys puluatris, Wagn., Suppl. Sclireber, iii. 1843, 543. 



Hesperomys {Oryzomys) palustris^ Bd., M. N. A. 1857, 483. 



Arvicola oryzivora, Aud. & Bach., Q. N. A. iii. 1858, 214, pi. 144, f. 3. 



Hab. South Atlantic and Gulf States, north to New Jersey. 

 Kansas! (Goss). Tchuantepec (>S'i<77u'c7i?-a.s(!). Jamaica? 



Genus IV. OCHETODON, Coues, n. g. 



Syn. Mus, sp., Aud. & Bach. Hesperomys^ sp., Wagner. Reitlirodon, 

 Le Conte, P. A. K S. P. 1853, 413, and Baird, M. N. A. 1857, 447, 

 hut not of Waterhouse. 



Diag. Form murine (general appearance of 3Ius musculus). 

 Size minute. Skull as in Vesperimus ; coronoid not attaining 

 level of condyle. Tail about as long as head aud body. Upper 

 incisors grooved (^unique character among N. American Ilurinx). 

 Front upper molars with four roots instead of three, as in Hespe- 

 romys. 



Obs. The occurrence in North America of sigmodont mice with 

 sulcate incisors was first noticed in 1841 by Audubon aud Bach- 

 man, who described 3Ius humilis. Their animal was soon referred 

 to Hesperomys b^^ Wagner. But the peculiarity of the upper 

 incisors was overlooked until 1853, when Maj. Le Conte took up 

 the point and referred a species to the South American genus 

 Reitlirodon a course followed by Prof. Baird in 1857, when the 

 latter described three supposed new species, R. moiitainis, mega- 

 lofis, and longicmida. But sulcation of the incisors is almost the 

 onl}' character that Ochetodon shares with Reitlirodon ; the two 

 genera are otherwise widely difterent.' 



Beithrodon, Waterh., P. Z. S. 1837, 29 ; Zool. Voy. Beag. 1839. Type 

 R. cuniculoides. 



DUig. Upper incisors sulcate. Rostral portion of the skull large in proportion to 

 the cranial, producing a high, convex forehead; zygomatic width of skull about its 

 length ; interorbital portion narrow ; posterior nares contracted from close approxi- 

 mation of the pterygoids ; palate with lateral paired fossse, and ending nearly opposite 

 or beyond the last molar; incisive foramina very long, extending to or beyond the 

 first molar ; coronoid process small and exflected ; condylar narrow and very oblique ; 

 descending process large, subquadrate, the emargination between this and the con- 

 dyle deep. Size large ; form stout and compact ; head broad and arched ; eyes large 

 and prominent ; ears moderate, pilous ; soles hairy behind j lateral toes subequal and 

 extremely short ; tail short, about one-half the head and body, moderately hairy. 



