356 On new dyptotis; Thomasomys, and Oryzomys. 



5'3 ; palatilar length 15-2; palatal foramina 8*2; upper 

 molar series 6 ; breadth of m} 1"5. 



IJcih. MeJelliii. Type from San Pedro, north of the town. 



2>/ve. Adult male. B.M. no. 21. 7. 1.20. Original num- 

 ber 9. Collected December 1919. One specimen. 



Tliis fine rat is a member of the T. aureus group, of which 

 I have before me examples of all the described species. Its 

 skull and, especially, its molars are so much smaller than the 

 corresponding parts in aureus that it clearly needs a new 

 name. The T. priiiceps of Bogold is larger than aureus, 

 wiiile Allen's 7\ poj)fit/a7iuii is of about the same size as the 

 latter, and is j)erhaps rather doubtfully separable from it. 



I have much jdeasure in naming this handsome animal in 

 honour of the naturalist to whom we owe its discovery. 



Oryzomys iniectus, sp. n. 



A small species with short tail, somewhat like O.balneator, 

 but with larger molars. 



Size rather lai-ger than in halneator. Fur soft and fine, 

 liairs of back about 7 mm. in len^^th. General colour above 

 uniform dark mouse-grey, very like that of Mus musculus^ 

 the hairs finely ticked with drabby. Sides more drabby. 

 Under surface slaty grey, tiie ends of the hairs dull whitish. 

 Face more blackisii, a blackish area round the eyes, b^luw 

 and behind which the light colour of the throat extends 

 rather high up towards the ear, forming a light whisker- 

 mark. Hands and feet whitish above. Tail unusually short, 

 apparently not as long as the head and body, very finely 

 haired, almost naked, brown above, dull whitish below. 



Skull peculiarly short, broad, and rounded, with broad 

 interorbital region. Indeed, it is almost precisely like that of 

 a Melanomys^ with the important exception that there is no 

 trace of the supraorbital beading so conspicuous in that group. 

 Brain-case similarly low, smooth, and without ridges. Palatal 

 . foramina short, about the length of the tooth-row. Molars 

 stout and heavy, large for the size of the animal, their struc- 

 ture more like that in Melanomys than in the smaller species 

 of Oryzomys, but many of the larger species of Oryzomys 

 also have quite similar molars. 



Dimensions of the type, measured on the skin : — 



Head and body 100 mm.; tail 91 ; hind foot (wet) 22. 



Skull: greatest length l'^'^; condylo-incisive length 23*5; 

 zygomatic breadth 14'2; na.-als 10*3 ; interorbital breadtli 5; 

 breadth of brain-case 12-2; i)alatilar length ll'I; palatal 

 foramina I"2 (4-6 in an older specimen) j upper molar 

 series I"2. 



