202 Field Museum or Natural History — Zoology, Vol. XL 



of molars tuberculate ; front of incisors with distinct longitudinal groove. 

 Total length, about 5 in. (120 to 130 mm.); tail vertebrae, 2 to 2.50 in. 

 (50 to 65 mm.). 



Genus ORYZOMYS Baird. 



Oryzomys Baird, Mammals N. Amer., 1857, p. 458. Type Mus palus- 



tris Harlan. 



Molars or grinding teeth with tubercles on crowns arranged in two 

 rows; hair on tail scanty; skull showing a distinct ridge over eye socket; 

 belly not white; hind feet large. 



Dental formula: I. ^— ^j C. ^— ^, Pm. ^— ^> M. ^-^= 16. 

 i-i 0-0 0-0 3-3 



Oryzomys palustris (Harlan). 

 Rice Field Mouse. Rice Rat. 



Mus palustris Harlan, Silliman's Amer. Jour. Sci. & Arts, XXXI, No. 2, 1837, p. 386. 

 Arvicola oryzivora Audubon & Bachman, Quadrupeds of N. Amer., Ill, 1854, p. 214. 

 Hesperomys (Oryzomys) palustris Baird, Mammals N. Amer., 1857, p. 459. 

 Oryzomys palustris Merriam, Proc. Wash. Acad. Sci., Ill, 1901, p. 276. Hahn, 



Ann. Rept. Dept. Geol. & Nat. Resources Ind., 1908 (1909), p. 640 (Indiana). 



Howell, Proc. Biol. Soc. Wash., XXIII, 1910, p. 26 (Illinois and Missouri). 



lb., p. 61 (Kentucky, Tennessee, etc.). Van Hyning & Pellett, Proc. Iowa 



Acad. Sci., XVII, 1910, p. 213 (Iowa). 

 Calomys palustris Evermann & Butler, Proc. Ind. Acad. Sci., 1893 (1894), p. 139 



Type locality — Fast Land, near Salem, Salem Co., New Jersey. 



Distribution — Southern United States, from southern New Jersey to 

 the northern border of Florida, westward throughout the Gulf 

 states, Tennessee and part of Kentucky, southern Illinois and 

 southern Missouri to Kansas, Oklahoma and eastern Texas. 



Special characters — Readily distinguished from a Peromyscus by its 

 long and more scantily haired tail, its large hind feet and decidedly 

 less abrupt line of demarcation between color of sides and belly, which 

 is gradual and not sharply defined, and from all other Rats or Mice 

 which occur within our limits either by its size or by the arrangement 

 of the tubercles on the crowns of the grinding teeth (two longitudinal 

 rows). It occurs within our limits only in southern Illinois. 



Description — Middle of upper parts from head to base of tail dark 

 brown shading into pale brown tinged with buffy on the sides; 

 under parts grayish, the hairs grayish plumbeous at the base and 

 tipped with white, but the grayish under fur showing through; 

 tail very scantily haired, dark above, pale below; feet whitish 

 (pinkish white in life). 



