Goldman — Five Neiv Rice Rats of the Genus Oryzomys. 129 



General characters. — A small form closely allied to Oryzomys alfaroi 

 alfaroi ; color of upper parts richer, more rufescent; skull usually nar- 

 rower. Similar to 0. gracilis and to 0. alfaroi pabnirx, but color more 

 rufescent and skull differing in detail. 



Color. — Type: General color of upperparts near ochraceous-tawny, 

 purest on cheeks shoulders and sides, the top of head and back suffused 

 with tawny, finely mixed with black ; underparts dull white ; ears black ; 

 feet white, the four longer toes of hind feet with tufts of silvery bristles 

 projecting beyond the claws. 



Skull. — Small and slender in form, the anterior palatine foramina 

 broad, but much shorter than palatal bridge; audital bullae small. About 

 like that of 0. a. alfaroi, but braincase and frontal region usually nar- 

 rower. Closely resembling that of 0. a. palmirse, but shorter, with 

 more widely spreading zygomata and smaller teeth. 



Measurements. — Type: Total length, 203; tail vertebrte, 107; hind 

 foot, 25.5. Average of five adult topotypes: 220 (212-226); 113 (107- 

 117); 24.6 (23-26). Skull (type): Greatest length, 27.4; zygomatic 

 breadth, 14.5; interorbital breadth, 5; length of nasals, 11.1; length of 

 anterior palatine foramina, 3.7; length of palatal bridge, 5.5; length of 

 upper molar series, 3.7. 



Remarks. — This small, slender rice rat differs from typical 0. a. alfaroi, 

 of Costa Rica, mainly in richer, more tawny coloration. It is closely 

 allied to the Colombian form described as 0. palmirx and the latter is 

 clearly assignable to subspecific rank, if it does not prove to be identical 

 with 0. gracilis, the type of which came from farther north in the Cauca 

 Valley. Comparison of 0. a. dariensis with specimens from northern 

 Ecuador, assigned to 0. gracilis by Mr. Oldfield Thomas, and reference 

 to the original description of that species indicate that the two are very 

 nearly related. The description of the color of 0. gracilis, however, 

 seems to apply to the Ecuadorean specimens, or to 0. palmirse, rather 

 than to the Darien animal. Moreover, the skull of the new form is dis- 

 tinguished from that of 0. gracilis, as here understood, by the greater 

 lateral expansion of the zygomata. 



Specimens examined. — Ten, all from the type locality. 



Oryzomys couesi regillus subsp. nov. 



Type from Los Reyes, Michoacan, Mexico. No. 125,945, male adult, 

 U. 8. National Museum (Biological Survey Collection), collected by 

 E. W. Nelson and E. A. Goldman, February 17, 1903. Original num- 

 ber 15,962. 



General characters. — A large richly colored form of the 0. couesi group, 

 with long, soft pelage. Similar in general to 0. c. couesi but much 

 larger and paler colored, the underparts usually white instead of buffy. 

 Size and proportions about as in 0. albiventer, but upperparts darker 

 and more rufescent in color. 



Color. — Type: Upperparts in general rich ochraceous-buff, the back 

 and rump strongly suffused with tawny and lined with black hairs; under- 



