476 Mr. O. Thomas on new 
Size about as in A. cinerea. Fur similarly soft and fine, 
hairs of back about 17 mm. in length. General colour above 
near Ridgway’s “ drab,” very uniform everywhere, the back 
little darker than the sides. Under surface greyish drab, the 
hairs broadly slaty for three-fourths their length, their tips 
pale drab ; hairs of sternal gland white to their roots. Chin 
greyish white; underside of neck stronger drab. Head 
without special markings. Hands and feet pure white, the 
latter of more normal length than in the curiously short-footed 
A. cinerea. Tail of medium length, iron-grey above, white 
below. 
Skull agreeing with that of A. cinerea in the normal 
minuteness and separation from each other of the posterior 
palatal foramina, as in the majority of rodents, while in 
A. bennettii and murray? these are of exceptional size and are 
fused into a single median foramen. Nasals markedly nar- 
rowed and pointed posteriorly. Malars not much expanded, 
but differing from others by being so twisted that, instead of 
forming a nearly vertical plate, their inner side can be broadly 
seen from above, facing upwards and inwards towards the 
supraorbital edges. Interorbital region very narrow, more 
so than in any other species. Bullee smaller than in either 
A. murrayt or cinerea. 
Incisors not so reduced as in A. cinerea, about as in 
A. bennettiz. Molars of the usual pattern. 
Dimensions of the type :— 
Head and body 201 mm.; tail 144; hind foot 31; 
ear 24°2. 
Skull: greatest length 50; condylo-incisive length 47; 
zygomatic breadth 24:5; nasals 20°5x5°5; interorbital 
breadth 6°4; least breadth across brain-case 20; palatilar 
length 22; diagonal length of bulla 16:2; bimeatal breadth 
25; upper cheek-tooth series (crowns) 10°2; dental length 
26°6. 
Hab. Otro Cerro, Catamarea. Alt. 3000 m. 
Type. Adult male. B.M. no. 20. 3.17.62. Original 
number 817. Collected 15th November, 1919, by E. Budin. 
Four specimens. 
“ Caught among.rocks, in the clefts of which it lives.”— 
Ei. B. 
This fine chinchilla-rat, as Sr. Budin calls it, adds to the 
genus Abrocoma a fourth and very distinct species, readily 
distinguishable externally by its colour and proportions, and 
cranially by its narrow interorbital region, small posterior 
palatal foramina, and the other characters above detailed. 
