276 MERRIAM 



In studying the species of Oryzotnys it is very necessary to 

 use skulls of fully adult and even old individuals, as in many 

 forms the specific characters do not develop until rather late in 

 life. The males are larger than the females and usually have 

 the characters more accentuated. The cranial characters that 

 have proved most useful are the form and thickness of the zygo- 

 matic arches, length and breadth of rostrum, form of nasals, 

 degree of development of supraorbital (or superciliary) beads, 

 size and form of incisive foramina (or palatal slits), and size of 

 molar teeth. 



ORYZOMYS PALUSTRIS (Harlan). 



Mus palustris Harlan, Am. Journ. Sci. and Arts, xxxi. No. 2, pp. 385-386, 



1837- 

 Hesperomys {Oryzoviys) palustris Baird, Mammals N. Am., 482, 1857. 

 Oryzotnys palustris texensis Allen, Bull. Am. Mus. Nat. Hist., Vol. vi, 



177-179, May 31, 1894.1 



Type locality. — Southern New Jersey (near Salem, Delaware 

 Bay). 



Characters. — Size medium or rather large (about equaling a half- 

 grown house rat, which the animal greatly resembles) ; ears rather 

 small; tail rather short; color grayish; belly white. 



Color. — Upperparts grizzled grayish brown ; sides somewhat buffy ; 

 back copiously mixed with black hairs ; underparts white, the slaty 

 underfur showing through; tail dusky above, whitish below; feet 

 whitish. 



Cranial characters. — Skull of medium size, somewhat flattened, 

 with moderately developed superciliary beads; rostrum elongate; 

 nasals long and tapering, wedgeshaped, ending about on plane with 

 premaxillse ; zygomata rather narrow, their outer sides nearly parallel ; 

 palatal slits exceedingly long. Skull very like that of mexicatius 

 but flatter, nasals longer and less decurved ; palatal slits longer. 



Measurements. — Average of 9 specimens from Raleigh, N. C. : 

 total length 231 mm. ; tail vertebrce 117; hind foot 29. 



Note. — In the absence of specimens from the type locality (south- 

 ern New Jersey) the above description has been drawn from speci- 

 mens from Dismal Swamp, Va., and Raleigh, N. C. 



' I am unable to distinguish Allen's subspecies texensis, either externally or by 

 the skulls, from O. palustris from Raleigh, N. C, and Dismal Swamp, Va. 

 The braincase may average a trifle narrower, but the difference is very slight. 



