neio Neotropical Mammals. 279 



back, dull rufous fawn, finely lined with blackish ; muzzle, 

 cheeks, and sides greyer and paler. Region between eye and 

 ear blackish. Ears large, naked, grey. Underside of neck, 

 throat, chest, and inner sides of fore limbs white; belly and 

 inner sides of hind limbs dirty whitish buff, the hairs grey 

 basally, whitish terminally. Metapodials brown above, but 

 their inner edges and the whole of the digits white. Tail 

 dark for its basal and white for its distal half, but the junction 

 of the colours is very irregularly mottled, the dark mottling 

 extending above towards the end, while the white extends 

 below more towards the base of the tail. 



Skull broad and heavy, much broader and heavier than in 

 T. panamensis. Nasals almost parallel-sided, square-ended 

 posteriorly, decidedly surpassed by the premaxillfe; supra- 

 orbital ridges well-developed, diverging evenly and broadly 

 outwards, without postorbital projection, the parietal portion 

 strongly convex outwards, so that the broadest place on the 

 ridges is just behind the zygomatic root instead of in front 

 of it. 



Dimensions of the type (an adult female, measured by 

 collector in the flesh) : — 



(Total length 493 millim.*) Head and body 250 ; tail 243 ; 

 hind foot s. u. 35, c. u. 38 ^. 



Skull : greatest length 54 ; basilar length from heu- 

 selion 42*5 ; greatest breadth 26"5 ; nasals, length 18 ; inter- 

 orbital breadth 10*5 ; breadth across most distant points of 

 parietal ridges (near middle of parietal) 20'5 ; palate length 

 from henselion 22'2 ; diastema 15"3 ; length of upper molar 

 series 8"4. 



Hah. Bogava, Chiriqui, N.W. Panama, alt. 250 ra. 



Type collected Sept. 6, 1898, by H. J. Watson. Original 

 number 7. Two specimens examined, adult and young. 

 " Caught on banks of river." 



This handsome TyJomys is most nearly allied to the 

 Guatemalan T. nudicaiidatuSy Pet., but is more rufous, its 

 posterior belly is not white, but soiled greyish, its muzzle and 

 nasal bones are longer and broader, and its parietal ridges are 

 more uniformly and widely bowed outwards. 



* As a step towards a greater uniformity in measuring I propose, in 

 agreement with certain of the Americfin zoologists, to record " total 

 length " and the cum wngtie hind-foot measure for all animals described 

 north of the Isthmus of Panama, while they for their part will give 

 " head and body '" and the sine ungue foot measure for animals described 

 from bevond North-American limits. 



