404 Mr. 0. Thomas on some Mexican Oiyzomys. 



distance. Lips, cliin, throat, and inguinal region whitish, 

 belly with a strong suffusion of fawn, which reaches a maxi- 

 mum on the breast between the fore legs ; passage of upper 

 colour into lower quite gradual. Outer sides of limbs like 

 back, inner sides whitish ; upper surfaces of hands and feet 

 thinly clotlied with pale silvery-fawn hairs. Tail long, thinly 

 haired, the scales not hidden by the hairs ; above blackish, 

 below yellowish, darkening towards the tip. 



Skull readily distinguishable from all allied species by its 

 great breadth, the bold expansion of the zygomata, and 

 especially by the evenly incurved outline of the supraorbital 

 edges ; in all other species these edges form two approxi- 

 mately straight lines diverging from the narrowest interorbital 

 point, but in O.fidgens the whole inner wall of the orbit forms 

 one even curve, the breadth at the posterior end of the olfac- 

 tory chamber being scarcely greater than at the anterior end. 

 Nasals broad and flattened. Frontal premaxillary processes 

 very narrow and barely attaining to the same level as the 

 back of the nasals. Anterior palatine foramina large, widely 

 open, their posterior margin just level with the front of ?l^. 



Measurements of the type (an adult male in skin) : — 



Head and body 160 millim. ; tail 151 ; hind foot, without 

 claw 35, with claw 37'5 ; ear (approximate) from notch 13"3. 



Skull (see below). 



Hah. Mexico. Coll. A. Boucard. 



Type B.M. 70. 6. 20. 3. Purchased of Geale. 



As already noted, this species is founded on specimen h of 

 Mr. Alston's description of Heaperomys Couesi. Its exact 

 locality unfortunately must remain unknown until further 

 specimens of it are found ; but its characters, both external 

 and cranial, are so striking that I have no hesitation in 

 describing it as a distinct species. 



Oryzomys melanotis, sp. n. 



Size small^ form more slender and delicate than in the 

 allied species. Fur straight, close and crisp. General colour 

 grizzled rufous, brighter and clearer on the sides and rump. 

 Lips, inner sides of limbs, and whole under surface white, the 

 line of demarcation on sides well defined ; the belly-hairs are, 

 however, as usual slaty grey basally. Ears large, projecting 

 far beyond the fur, closely covered with short black hairs^ 

 their black colour contrasting conspicuously with the general 

 rufous colour of the head. Upper surfaces of hands and feet 

 whitish. Tail long, very scantily haired, blackish above, 

 whitish below. 



