South- American Rodents. 445 



to be proportionally larger, more rounded, and Rht'pidomys- 

 like. Feet broad, suited for climbing; fifth hind toe propor- 

 tionally long. Tail with the body-fur encroaching on its 

 base for half an inch or more ; terminal part well iiaircd — 

 more so than in true Oryzomjjs — and generally pencilled, 

 though never so heavily as in Rhipidomi/s. 



Type. Rhipidomi/s benevolens, Thos. 



The following is the list of species belonging to this 

 group : — 



Oryzomys {(Ecomys) hicolor^ Tomes. 



( ) dryas, Thos. (probably = 6ico^or). 



( ) benevolens, Thos. (Type.) 



( ) marnwsurus^ Thos. 



( ) mamorce, Thos. {infra). 



phieotis, Thos. 



( ) paricola, Thos. 



( ) rosilla, Thos. 



( ) Bobertij Thos. 



Rhipidomys rufescens, Thos., also probably belongs to 

 (Ecomys, but the essential parts of the type skull have unfor- 

 tunately been broken away. 



In the transference of these species to Oryzomys only one 

 name — dryas — clashes with a term already in use in that 

 genus. But it so happens that this animal is probably the 

 same as Tomes^s bicolor, which, as the type now shows, was 

 described from a discoloured specimen with a broken tail, 

 while my distinction of dryas was based on the difference oi: 

 colour and the longer tail as compared with Tomes^s descrip- 

 tion, the type not being then available for examination. 



With regard to jSyctomys, hitherto somewhat doubtfully 

 separated from Rhipidomys, I am able to point out an 

 important character which wull distinguish it from that genus. 

 This is that the first upper molar, instead of being evenly 

 oblong, with six subequal cusps, has only five well-developed, 

 the antero-internal one being almost or quite obsolete. The 

 group may therefore possibly be an offshoot of the Fero- 

 7nyscus stock, with no close relationship to Rhipidomys at all. 



III. — A 7ieio CEcomys and Two new Species of Holochilus. 



Oryzomys {(Ecomys^ mamorce, sp. n. 



One of the largest species of the group, as large as a 

 medium-sized Rhipidomys, about the same size as O. {(E.) 

 marmosuriis. Hairs of back about 10 mm. in length. 



Ann. ii; Mag. X. Hist. Ser. 7. Vol. sviii. 33 



