O'J^ 



250 Mr. O. Thomas on a neio Species of Hesperomys. 



affords me the opportunity of informing him that Dr. Giinther, 

 since he has had living specimens of E. arvalis and R. agilis 

 for examination, now also adopts the view that thej deserve 

 specific distinction. 



And now I have only to add that, of the numerous speci- 

 mens from various European localities which have passed 

 through my hands since the publication of my Revision of 

 the Ranee temporaruej I have not met with a single one which 

 I have not been able to pronounce at first glance as belonging 

 to one or the other of the European species. 



XXIV. — Description of a neio Brazilian Species o/Hespe- 

 romys. By Oldfield Thomas, Natural-History Museum. 



Among a small series of mammal-skins sent over from Rio 

 Janeiro to Mr. E. Gerrard, Jun., occurs a specimen repre- 

 senting a striking new species of Hespcromys, which I propose 

 to call 



Hesperomys rufescens^ sp. n. 



General colour rich orange-rufous all over, both above and 

 below, the hairs everywhere slaty blue at their bases and 

 rufous at their tips. Underside only slightly lighter than 

 upper. Ears short, scarcely projecting beyond the fur, thickly 

 covered with rufous-brown hairs. Feet yellow ; toes whitish, 

 fifth hind toe to end of second phalanx of fourth. Tail of 

 medium length, unicolor, thinly covered with brown hairs, 

 which form an inconspicuous pencil at the tip. 



Skull with the cranial portion very large ; interorbital region 

 broad. Supraorbital edges square, not ridged. Incisors 

 dark orange above, yellow below. 



Measurements of the typical skin (female) : — Head and 

 body 94 millim., tail 93, hind foot 20'0, ear (above crown) 

 (c.) 7-0. 



Skull: basal length (c.) 25'5, zygomatic breadth 16*8, 

 length of face 15'0 ; brain-case, length (c.) 13*0, breadth 

 14'2 ; interorbital breadth 5"1 ; nasals, length 9*0 ; back of 

 incisors to m^ 8'0 ; length of molar series 4"9 ; palatal fora- 

 men, length 4-3, 



Hah. Rio Janeiro. 



Although superficially much resembling the smaller species 



of the Oryzomys section of Hesperomys, this species has only 



one really near ally, viz. H. hicolor, Tomes*, a native of 



Ecuador, which differs from it by its white belly and naked 



• P.Z.S. 1860, p. 217. 



