114 Mr. O. Thomas on 



Dentition above not specialized, in some ways very like a 

 miniature of that of Erethizon. 



Other external characters described below. 



Skull so like that of Mesomys hispidus that it is difficult to 

 find any character of more than specific value. The muzzle 

 is broader, the nasals being more parallel-sided, less tapered 

 backwards. Interorbital region broad, with overhanging 

 led°es. Brain-case low, smooth above, much broadened 

 posteriorly. Malar more projected forward anteriorly than in 

 Mesomys, about as in Echimys. Palatal foramina longer and 

 more open than in Mesomys. Mesopterygoid fossa narrow, 

 reaching forward to the level of the middle of m 2 . Hamular 

 processes of pterygoids narrow, scarcely spatulate at all. 

 Bullae of average size. 



Incisors strong, deep from before backwards, less opistho- 

 dont than in allied forms, the incisive angle of the type- 

 specimen 93°. 



Upper cheek-teeth about as broad as long, of medium 

 height, not hypsodont, each with two salient angles internally 

 and four externally, the last external with an indication of 

 subdivision, so that the full number of enamel-plates is, as 

 usual, five. The height of the crests and the depth of the 

 valleys between them very much as in Erethizon, to whose 

 teeth those of Lonchothrix bear a strong resemblance in 

 miniature, though the hollows are more linear, less broadened 

 antero-posteriorly. Outer valleys penetrating about two- 

 thirds across each tooth. Below the resemblance to Erethizon 

 disappears ; p± has five crests on its inner half, m 1 three and 

 an imperfect fourth, w 3 and m 3 three ; all have, as usual, one 

 deep outer notch separating the two salient angles. 



Although less specialized, the teeth have also a certain 

 resemblance to those of Gercomys. 



Genotype. Lonchothrix emilice, sp. n. 



It is difficult to say to which of the described forms this 

 striking new genus is most nearly allied. Its short climbing 

 feet and strongly spinous coat give it a general resemblance 

 to Echimys, but its brachyodont molars, as broad as long, are 

 very different from those of either Echimys or any of the 

 genera allied to it — such as Nelomys and Diplot/trix, — nor 

 have they any of the high specializations found in Dactylomys 

 and Kannabateomys ; and its tufted tail is peculiar to itself. 



Lonchothrix emilice, sp. n. 

 Size about as in Mesomys hispidus. Pelage excessively 



