16 



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



Syn. Mus palustris Harl., Am. Journ. Sci., xxxi. 1837, 386 (New Jersey). 



Hesperomys palustris, AVagn., Suppl. Schreber, iii. 1843, 543. 



Hesperomys {Oryzomys) palustris, Bd., M. N. A. 1857, 482. 



Arvicola oryzivora, Aud. & Bach., Q. N. A. iii. 1853, 214, pi. 144, f. 3. 



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

 Kansas! {Goss). Tehuantepec (Sumichrast). Jamaica? 



Genus IV. OCHETODON, Coues, n. g. 



Syn. Mus, sp., Aud. & Bach. — Hesperoinys, sp., Wagner. — Reithrodon, 

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

 but not of Waterhouse. 



Diag. Form murine (general appearance of Mus musculus). 

 Size minute. Skull as in Veaperimus ; coronoid not attaining 

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

 incisors grooved (unique character among N. American Murinse). 

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

 romys. 



Obs. The occurrence in North America of sigmodont mice with 

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

 man, who described Mus humilis. Their animal was soon referred 

 to Hesperomys l)y 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 

 Reithrodon — a course followed by Prof. Baird in 185T, when the 

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

 lotis, and longicaiLda. But sulcation of the incisors is almost the 

 onl}^ character that Ochefodon shares with Reithrodon ; the two 

 genera are otherwise widely different.' 



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

 R. cuniculoides. 



Diag. 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 fossae, and ending nearly opposite 

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

 first molar j 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 I ears moderate, pilous ; soles hairy behind ) lateral toes subequal and 

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



