from Brazil and Ecuador. 19'> 



Proechimys oris, sp. n. 

 Most rearly allied to P. cayemiensis and P. RohertL _ 

 General proportions about as in P. oyennensis. bpines ot 

 back more restricted in their distribution than in that species, 

 the posterior back for nearly a third of its lengtii being 

 spineless : thighs, flanks, and nape also practically without 

 spines. Spines of back about 18 mm. long by O"? mm. 

 broad. Lower belly and inner sides of forearms and thighs 

 nearly naked. General colour above dark tawny brown, 

 lined with blackish, the soft-haired rumo more rutous ; heart, 

 sides, arms, and h-gs greyish brown. In P. cajjennenszs the 

 general colour is darker, the rump brovvnish and tjie back 

 of the hind legs heavily blackened. Hands and ieet dull 

 whitish, without special markings, lail large-sc.iled, thinly 

 haired, brown above, whitish below. 



Skull very like that of P. cayennensi'^, but rather more 

 slender. Interparietal longer antero-posteriorly. Anterior 

 edge of malar forming a long, sharp, forwardly projecting 

 angle at its junction with the maxillary, the corresponding- 

 line in P. cayennensis being short and obtuse \'^\^!^^\ 

 foramina w.U open mesially, but narrowing rapidly behind 

 almost to a point, witii little trace of such raised edges as in 

 P. cayennensis form two parallel open gutters behind. 13ase 

 of skull between bullfe narrower than m cayennensis. 



Teeth as in P. cayennensis, the upper ones all simply and 

 uniformly quadrilaminate. 



Dimensions of the type (measured by Mr. Rooert in the 



flesh) : — ., „ , , • 1 J- ^ / \ Ai" . 



Head and body 245 mm. ; tail 1<4; hind fuot (s. u.) 4b, 



ear 21. . ., , i i-. >.• 



Skull: greatest length 58 ; basilar length 41 ; zygomatic 



breadth 26; nasals 21-5; interorbital breadth 12; breadth 



across parietal ridges 21 ; palate length 19-5 ; diastema 11 8 ; 



palatal iorannina 7x3-2; length of upper tooth-series h' L 

 Hah. Igarape-Assu, near Para. Alt. 50 m. 

 Type. Old male. B.M. no 4. 7. 4. 78. Original number 



1818: Collected 6tli March, 1904, by Alphonse Kobert. 



Seventeen specimens. . r i • i ^-i 



This spiny rat differs from V . cayennensis o\ ^ I'ch the 

 British Museum contains four topotypes obtained by Mr. G. K. 

 Cherrie, by its more rufous colour, especially its much more 

 reddish rump and hind limbs, by the lesser spininess of its 

 posterior back, by the nakedness of its inguinal region, and 

 by the cranial characters above detailed 



Another allied species is P. lioherti, Thos., of S. Minas 



