1882. ] MR. 0, THOMAS ON RODENTS FROM PERU. 105 
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 
linch long. I am therefore inclined for ‘the present to continue to use 
Bennett’s well-known name, believing that 4. longitarsus may be 
found to be only the youug form of some larger species. 
7. Hesperomys (CALOMyYs) SPINOSUS, sp. n. 
a, b. Huambo, 3700’, April and May 1880. 
Head and Forearm LEar-conch, Muzzle 
body. Tail. Hind foot. andhand. length. to ear. 
Ghid hie3°0! 3°85 87 "95 50 ‘78 
Bordnned:0 3°95 87 “94 "46 ‘75 
Back of Breadth of con- 
Total Greatest Molar incisors to striction between Lower jaw 
length breadth. series, Ist molars. orbits. (bone only), 
Skullofa..:°91 ‘51 13 22 ‘19 50 
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. Lars thinly 
covered with 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 mamme ; 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- 
1 Taken before the skull was extracted, 
