236 ^ly. (^- Tlionms on some 



curious how {cw tangible characters can be drawn from tlie 

 skulls, while the teeth, as is the usual difficulty in the 

 Akodun-Oxymycterus group of genera, give ))ractically no 

 help at all. 



The following are the three genera I propose to recognize : — 



Oxymyclerus, Waterhouse. 



Fore claws elongated, fossorial ; nail of poUex narrow, 

 pointed. Muzzle long, mobile. Tail much shorter than 

 head and body (about two-thirds). 



Siaill with a long muzzle, the nasals produced forwards in 

 old specimens and expanded anteriorly, so as to make a more 

 or less trumpet-shaped opening, their ))osterior end anterior 

 to the front of the orbit. Zygomatic plate narrow, slanting, 

 its anterior edge sloping all the way down to its junction 

 with the maxilla. Brain-case large, smooth, rounded, con- 

 trasting with the long slender muzzle. 



Bange. Brazilian region, extending westwards into Peru 

 and south to La Plata. Not known north of the Amazon. 



Type. 0. nasu(us, Waterhouse. Other species : 0. rvfus, 

 Desm.*, hi'spidus, Pict., jidiacce, All., rostellatus, Wagn., 

 qucBstor, Thos., delator^ Thos., inca, Thos., &c. 



Lenoxus, gen. no v. 



Form normal, rat-like, muzzle not specially elongated. 

 Fore claws of moderate size, not fossorial ; nail of pollex not 

 pointed. Tail about the length of the head and body. 



Skull more normal in shape, and though the muzzle is 

 long, it is bread and heavy proximally and tapers distally ; 

 nasals not expanded anteriorly, but reaching posteriorly 

 behind the front edge of the orbit. Interorbital region 

 swollen, rounded. Zygomatic plate narrow as in all this 

 group, but its anterior edge turns vertically downwards before 

 uniting with the maxilla. Brain-case not large in proportion 

 to the muzzle. Interparietal well developed. 



* I had been disposed to demur to the common reference of Desmarest's 

 Mus rufus to Oxymycteriis, as this was based solely on the " Rat roux " 

 of the French edition of Azara, and there the animal is said to have a 

 Bomewhat blunt nose, being even compared to the European Water-Vole. 

 But the precise agreement of Azara's description with examples of Oxy- 

 wycterus from this region both in proportions and colour now makes me 

 think that the nose ol his specimen, which was preserved in spirit and 

 then half dried up, must have got contracted or distorted, perhaps through 

 pressure against the sides of the bottle. Azara's "Hocicudo" of the 

 Spanish edition is unquestionably an Oxymyctenia, and his opinion that 

 the two -vrere the eame species may be accepted as correct, 



