406 Mr. 0. Thomas on 



while cursor, Winge, appears to represent a darker subspecies 

 occurring in the southern provinces. The new term is distin- 

 guisliable from both by its mucli paler and more buffy colour 

 and its slightly narrower skull. 



Akodon cerosus, sp. n. 



A. caliginosus, Tomes, of Allen * and Thomas f, nee 

 Hesperomys caliginosus, Tomes, wliicli is an Oryzomys. 



A large dark-coloured species practically indistinguishable 

 externally from Hesperomys (^Melanomys) caliginosus. General 

 colour above dark bistre-brown, little paler below. Ears, 

 hands, feet, and tail blackish brown. 



Skull that of a true Akodon ; with broad iuterorbital region, 

 smooth, unbeaded supraorbital edges, and evenly convex 

 upper profile. Anterior edge of zygomatic plate slightly con- 

 cave. Palatal foramina long, widely open, with smoothly 

 rounded edges. Teeth typical I3' Akodont. 



Dimensions of the type (measured in flesh) : — 



Head and body 108 mm.; tail 75 ; hind foot 24; ear 16. 



Skull : greatest length 29*3 ; condylo-incisive length 26*8 ; 

 zygomatic breadth 15; nasals 11; interorb'tal breadth 6; 

 breadth of brain-case 13 ; palatilar length 12*1 ; palatal 

 foramina 6' 6 ; upper molar series 4*9. 



Hab. Andes of Ecuador, Peru, and Bolivia. Type from 

 Mirador, Baiios, Ecuador. Alt. 1500 m. 



Type. Adult male. B.M. no. 99. 9. 9. 105. Original 

 number 234. Collected 6th February, 1899, by P. O. Simons. 

 Presented by Oldfield Thomis. About thirty specimens 

 examined. 



The two dark Andean species, one of Akodo7i and the other 

 of Oryzomys, subgenus Melanomys, being practically indis- 

 tinguishable externally, and Mr. Tomes's description of his 

 " Hesperomys caliginosus " agreeing equally well with 

 either of them |, both Dr. Allen and I took the description 

 as applying to the Akodon, though admitting that the 

 question could only be settled by an examination of Tomes's 

 type. 



" That type being now in the Museum (B.M. no. 7. 1. 1. 128), 

 I find that, unfortunately for our powers of divination, it is 

 unquestionably an Oryzomys, and presumably identical with 

 my 0. phceopus, the type of the subgenus Melanomys. As a 

 consequence, the Akodon needs a new name. 



* Bull. Am. Mus. N. H. iii. p. 210 (1891). 



t Aun. & Mag. Nat. Hist. (6) xiv. p. 356 (1894). 



X P. Z. S. 18C0, p. 263. 



