384 Mr. 0. Thomas on some 



contour of the skull. Supraorbital edges rounded. Palatine 

 foramina reaching to the middle internal prominence of m - l - 



Dimensions of the type (a skin) : — 



Head and body (c.) 110 millira. ; tail 85. 



Of an old male in spirit from the same locality : — 



Head and body 95 ; tail 75 ; hind foot 22 ; ear from notch 

 15'3 x 13 ; heel to front of last foot-pad 9*5. 



Skull (of the spirit-specimen) : greatest length 27, basal 

 length 24*2, basilar length 22*5, greatest breadth 14 ; nasals 

 9'3 x 3*6 ; interorbital breadth 5*1; interparietal 1*5 X 66 ; 

 palate length to henselion 12 ; diastema 7'6 ; palatal foramina 

 6x2"4; length of upper molar series 4*2. Lower jaw: 

 condyle to incisor-tip 17*6; tip of coronoid to angle 7; 

 height of ramus below ^\ 3" 6. 



Hab. Tumbez, N.Peru. Coll. Dr. J. Stolzmann. There 

 are also specimens in the Museum collection from Maraynioc 

 (Jelski) and Vitoc (Kalinowski) . 



Type: B.M. No. 85.4.1.49. 



This species is evidently the northern representative of 

 A. olivaceus, which ranges over Bolivia, Chili, and Pata- 

 gonia, and which it replaces in Ecuador and Peru. In dis- 

 tinguishing the two, I have examined six skulls of the 

 northern and ten of the southern form. 



Peromyscus* leucurus, sp. n. 



Size large, slightly less than that of P. mexicanus or P. cali- 

 fornicus. Fur soft and close, the hairs on the back 7 or 8 

 millim. in length. General colour cinereous grey, finely lined 

 on the back with blackish, clearer on the sides, where it is 

 approximately " drab-grey " of Ridgway. Chin white, rest 

 of under surface tl grey no. 8;" the bases of the hairs slate, 

 the tips white. Eyes without any prominent dark ring round 

 them, although the extreme edges of the lids are, as usual, 

 black. Ears large, but not so large as in P. Truei or 

 P. californicus, finely hairy, blackish brown. Hands and 

 feet white ; fifth hind toe, as in most other Peromysci, reaching 

 to the middle of the second phalanx of the fourth. Tail long, 

 more thinly haired than usual ; brown above and whitish 

 below for the proximal, wholly white all round for the distal 

 half ; a few hairs at the extreme tip are, however, brown. 



Skull, for a Peromyscus, strong and well built, most similar 

 in its proportions, of those available for comparison, to that 



* Gloger, 1841.— Syn. Sitomys, Fitz. 1867. An analysis of Gloger's 

 generic names is now in course of preparation, and -will be published 

 shortly. 



