300 Mr. O. Thomas on new 



Proechimys Simonsi, sp. n. 



Size rather smaller than in P. chrysceolus, its nearest ally. 

 Rump practically spineless ; nape and sides also much less 

 spinous than the centre of the back. Spines short, only 

 about 15 millim in length, and narrow (0'6-0*8 millim. in 

 breadth). General colour above very like that of P. rosa, 

 with the same grizzled mixture of black and fulvous. Head 

 rather darker and less fulvous. Under surface and inner- 

 sides of limbs pure sharply denned white, much more sharply 

 denned than in the allied species. Upper surface of feet dull 

 brown, lighter along the inner margins. Tail of about the 

 same length as in P. rosa and chrysceolus, but much less 

 hairy, the hairs not hiding the scales ; scales unusually large, 

 the rings running about 8 to the centimetre ; its colour promi- 

 nently bicolor, black above, white below. 



Skull remarkably like that of P. brevicauda, Giinth., 

 although in external characters the species has little re- 

 semblance to that animal. In size it is smaller than in any 

 of the species mentioned. Nasals long, narrow, rounded 

 behind, extending about 2*5 millim. beyond the premaxillse 

 posteriorly. Interorbital region narrow. Parietal ridges 

 almost obsolete, a faint indication of them in the positions 

 described in P. chrysceolus, not continuous as in P. rosa. 

 Palatal foramina broad and rounded, almost as broad as long, 

 the ridges on the palate just behind them nearly obsolete. 

 Palate emarginate to the back of m. 2 . Pterygoid processes 

 narrow, curved, not spatulate. Molars small and rounded. 



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

 flesh) :— 



Head and body 210 millim. ; tail 165 ; hind foot, s. u. 

 47, c. u. 49; ear 26. 



Skull : greatest length 53*2 ; basilar length 36'5 ; zygo- 

 matic breadth 25'3 ; nasals 20 X 5'5 ; interorbital breadth 

 11*3; greatest breadth on parietal ridges 20 j interparietal 

 7*5 X 12*2; diastema 10*4; palatal foramina 4*3 X 3*5; 

 length of molar series 7*5. 



Hab. Perene* River, Junin Province, Peru. Altitude 

 800 m. 



Type. Adult male. B.M. no. 0. 7. 7. 50. Original 

 number 942. Collected 14th April, 1900, by Mr. Perry O. 

 Simons. " Eaten by natives. Found in deep woods. 

 Native name ' Pericota.' " 



This species presents the curious anomaly of being closely 

 similar externally to P. chrysceolus and rosa, while its skull is 

 scarcely distinguishable from that of the outwardly very 



