1882.] MR. O. THOMAS ON RODENTS FROM PERU. lO.T 



foot no less than 14 lines in length, while the very largest specimen 

 in our considerable series of this species has a hind foot barely 

 1 inch long;. I am therefore inclined for ;the present to continue to use 

 Bennett's well-known name, beheving that H. longitarsus may be 

 found to be only the young form of some larger species. 



7. Hesperomvs (Calomys) spinosus, sp. n. 

 a, b. Huambo, 3700', April and May 1880. 



Back of Breadth of con- 

 Total Greatest Molar incisors to striction between Lower jaw 

 length breadth, series. Ist molars. orbits. (bone only). 



Skull of «.. -91 -51 -13 -22 -19 •SO 



Fur of medium length, composed of flattened spines intermixed 

 with fine hairs, the spines predominating on the back but becoming 

 rather fewer on the sides and disappearing on the belly. General 

 colour above dark grizzled rufous and black, the spines slate-coloured, 

 with black tips, the hairs also slate-coloured for the greater part of 

 their length, but their tips rich orange. Sides becoming paler towards 

 the belly, where the tips of the hairs in one specimen are white, 

 and in the other pale fulvous, the bases of the hairs, however, being, 

 as usual, slate. Head like back, but with fewer spines. Ears thinly 

 covered Avith short black hairs. Tail at its base dark brown above and 

 white below ; but the two colours soon merge into uniform blackish 

 brown ; the scales proportionally very large. Tail-hairs very scanty, 

 except at the tip, where they form a slight and inconspicuous pencil. 

 Fore feet dark brown, the toes slightly paler. Hind feet and toes 

 pale greyish white, not sharply separated from the colour of the 

 legs, with a brown patch on the distal part of the metatarsus. Foot- 

 pads small but prominent, soles smooth on proximal and granulated 

 on distal halves. Fifth hind toes, without claws, reaching barely to 

 the middle of the first phalanx of the fourth toes. Ears with a well- 

 marked projection on their anterior edge. Both the specimens 

 being males, I cannot record the number of mammae ; but the other 

 characters being so similar to those of ordinary Calomys, it is unlikely 

 that there would be any other number but 8. 



Skull on the whole similar to that of other small Calomyes, but with 

 the supraorbital ridges sharper and more strongly developed than 

 in any others that I have seen, and the space between the orbits 

 broader than usual. 



The discovery of this Mouse, as spiny as an average Heteromys, is, 

 as mentioned above, of great interest; for hitherto no spiny Hespero- 



^ Taken before the skull was extracted, 



