ARBOREAL RICE RATS — HERSHKOVITZ 545 



range of the species. It is a medium-sized, brightly colored form 

 with an irregular pattern of geographic variation that reflects seasonal 

 and local climatic differences. Nevertheless, individual variation in 

 any one locality may be of the same magnitude as variation within the 

 subspecies as a whole. 



The remaining four subspecies occupy peripheral and ecologically 

 distinct parts of the range of the species. Oryzomys concolor superans 

 Thomas, of the Amazonian rain forests along the base of the Andes, is 

 the darkest and largest race. 0. c. speciosus J. A. Allen and Chapman 

 of the northeastern bulge of South America resembles superans in 

 color, especially of the underparts, but agrees with typical concolor 

 in size. The palest subspecies, 0. concolor roberti Thomas, lives in the 

 subhumid southern border of the range in Bolivia and south-central 

 Brazil. 0. concolor bahiensis (new subspecies) is a saturate form of the 

 rain forests of eastern Brazil. 



The pattern of local and geographic variation in Oryzomys concolor 

 contrasts sharply with the comparative stability of 0. bicolor. The 

 difference between the two species in their response to color of soil 

 and cover, humidity and temperature may be attributed to slight but 

 significant differences in their habitat preferences. Oryzomys concolor 

 generally nests lower and descends to the ground with greater fre- 

 quency. It is, accordingly, less independent of factors controlling 

 living conditions at ground level. 



Oryzomys (Oecomys) concolor concolor Wagner 



Hesperomys concolor Wagner, Arch. Naturg., vol. 11, pt. 1, p. 147, 1845; Abh. 

 Akad. Wiss., Munich, vol. 5, p. 311, 1848 (characters)— Pelzeln, K. K. Zool.- 

 Bot. Gesellsch., Wien, Beiheft 33, p. 70, 1883 (characters; habits).— Gylden- 

 stolpe, Kungl. Svenska Vet-Akad. Handl., ser. 3, vol. 11, p. 151, 1932 (in- 

 certae sedis). — J. A. Allen and Chapman, Bull. Amer. Mus. Nat. Hist., 

 vol. 5, p. 213, 1893 (comparison with Oryzomys speciosus "with which it may 

 prove to be identical"). 



[Oryzomys] concolor, Tate, Amer. Mus. Nov., No. 579, p. 3, 1932 (taxonomic 

 history). 



Oryzomys flavicans Thomas, Ann. Mag. Nat. Hist., ser. 6, vol. 14, p. 351, 1894 

 (type locality, M^rida, Sierra de M^rida, Venezuela). 



0[ryzomys] flavicens [sic], Goodwin, Bull. Amer. Mus. Nat. Hist., vol. 102, p. 310, 

 1953 (lapsus for flavicans Thomas, in discussion of 0. palmarius J. A. Allen). 



Oryzomys flavicans illeclus Bangs, Proc. Biol. Soc. Washington, vol. 12, p. 164, 1898 

 (type locality, Pueblo Viejo, Sierra Nevada de Santa Marta, Magdalena, 

 Colombia, altitude, 853 meters. — Bangs, Proc. New England Zool. Club, 

 vol. 1, p. 94, 1900 (Colombia: La Concepci6n; Pueblo Viejo; Palomino; 

 San Antonio; Oryzomys trichurus J. A. Allen, part, a synonym). 



0[ryzomys] flavicans illeclus, J. A. Allen, Bull. Amer. Mus. Nat. Hist., vol. 12, 

 p. 206, 1899 (Minca, Santa Marta Region, Magdalena, Colombia). 



Oryzomys illeclus, J. A. Allen, Bull. Amer. Mus. Nat. Hist., vol. 20, pp. 436, 439, 

 1904 (Don Amo, Magdalena, Colombia). 

 504676—59 3 



