1834.] MUHID.E FROM CENTRAL PERU. 449 



Calomys, Waterhouse. — Form cricetine ; tail short, hairy ; Air 

 very long and soft ; feet small and slender, soles thickly 

 hairy; mammae 2-2 = 8. 



Skull slightly made ; interparietal very narrow from before 

 backwards; interorbital edges square; palatine foramina 

 Ions. 



Teeth as in the smaller Oryzomxjs. 

 Species: — II. 6imaculatu8,Wa.terh. (type), II. e/egans, Waterh., 



and II. gracilipes, Waterh. 

 Range. From Peru across the continent southwards to Buenos 

 Ayres and Bahia Blanca. 



Vesperimus, Coues. — Form murine; tail medium or long, thinly 

 hairy ; ears and feet large ; mammae 1-2 = 6. 



Skull generally lightly made, with large interparietal, 

 rounded or square supraorbital margins, little developed 

 anterior plate of zygoma root, and lung palatine foramina. 



Teeth with low complicated crowns, the folds generally 

 alternating on the two sides of each tooth. 

 Species : — H. leucopus, Raf. (type), H. californicus, Gamb., 

 II. aztecus, De Sauss., H. cinereus, Thos., H. taczunowskii, 

 Thos., &c, &c, about 10 in all. 

 Range. North America, southwards to Peru. 



Onychomys, Baird. — Form arvicoline ; tail and ears very short; 

 fore feet very large, with elongated claws ; hind feet short, 

 with hairy soles aud only four sole-pads ; mammas 0-2 = 4. 

 Skull and teeth much as in Vesperimus. 

 Species : — H. leucogaster, Wied. (type), and H. torridus, Coues. 

 Range. Southern United States. 



Scapteromys, Waterhouse. — Form murine ; tail long and hairy ; 

 feet unusually long ; thumb with a claw instead of a nail. * 



Skull and teeth much as in Habrothrix, but upper part of 

 infraorbital foramen larger, anterior plate more prominent, 

 and teeth broader and heavier. 

 Species : — H. tumidus, Waterh. (type), H. tomentosus, Licht. 

 Range. La Plata. 



Phyllotis, Waterhouse. — Form murine ; tail of medium length, 

 hairy; ears very large; feet short, soles naked; mammae 

 2-2 = 8 ; interdental palate-ridges 5. 



Skull with large interparietal, square or slightly beaded 

 supraorbital margins, long palatine foramina, and very pro- 

 minent zygomata. 



Teeth as in Habrothrix. 

 Species:—//, darwini, Waterh. (type), II. boliviensls, Waterhk, 



77. griseoflavus, Waterh., and //. xanthopygus, Waterh. 

 Range. Patagonian Subregion. 



1 Apud Petera, UA. Ak. Bert I860, p. 147. 



