518 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iio 



The first binomial for the smaller species of subgenus Oecomys is 

 Hesperomys hicolor Tomes, given in 1860 to a specimen from eastern 

 Ecuador. As in the case of 0. concolor, the true nature of hicolor 

 was not immediately appreciated by subsequent workers. The 

 next member of the species, collected in western Ecuador, was de- 

 scribed by Thomas in 1900 as Rhipidomys dryas. This was followed 

 by Rhipidomys phxotis, R. benevolens, R. rosilla and R. paricola, all 

 described by Thomas on the basis of comparisons with his R. dryas. 



In 1906, Thomas discovered the essential oryzomyine characters of 

 the small arboreal rice rats assigned by him to Rhipidomys. The 

 close relationship between them and Hesperomys hicolor Tomes was 

 also noted. Accordingly, Thomas combined them in Oecomys, a new 

 subgenus of Oryzomys. Thomas also included in subgenus Oecomys 

 his previously described marmosurus, mamorae, and roherti, each 

 based on a local form of the large species of arboreal rice rats. AU 

 other named forms of arboreal rice rats, including Hesperomys concolor 

 Wagner, were ignored or tacitly regarded as species of true Oryzomys. 



The name Oecomys was elevated to full generic rank by Thomas in 

 1909. This classification was followed by authors until Ellerman 

 (The families and genera of rodents, vol. 2, p. 342, 1941) questioned 

 the validity of Oecomys even as a subgenus. It appears that Ellerman 

 was misled by the current uncritical listing of some named forms of 

 Oryzomys concolor as species of typical Oryzomys, and other named 

 forms of 0. concolor as species of Oecomys. Thus, his specimens of 

 "Oryzomys" tectus and "Oecomys" osgoodi, exhibited as proof of the 

 absence of important differences between the two "genera" concerned, 

 are actually conspecific and identical with Oryzomys concolor. The 

 issue is further confused by Ellerman's observation that "Oecomys" 

 catherinae Thomas shares critical cranial characters with Oryzomys 

 suhflavus Wagner. The type of Oryzomys catherinae, however, is not 

 an Oecomys (see p. 543) but merely another specimen of Oryzomys 

 suhjlavus Wagner. The proper basis for evaluating the taxonomic 

 status of Oecomys is a comparison of its type species, 0. hicolor 

 Tomes, with 0. palustris Harlan, the type species of Oryzomys. 

 Neither of these species was taken into account by Ellerman. 



Recognized Forms of the Subgenus 



Oryzomys hicolor traheatus G. M. Allen and Barbour (p. 533). 

 Oryzomys hicolor occidentalis , new name for Rhipidomys dryas Thomas 



( = Oryzomys dryas Thomas), preoccupied (p. 533). 

 Oryzomys hicolor hicolor Tomes (p. 534). 

 Oryzomys hicolor phaeotis Thomas (p. 540). 

 Oryzomys concolor concolor Wagner (p. 545). 

 Oryzomys concolor speciosus J. A. AUen and Chapman (p. 553). 



