a new Mexican Oiyzomys. 179 



Ti/pe B. M. 110. 97. 12. 26. 1. Collected by Mr. H. H. 

 Smith, and presented by llr. F. DuCane Grodman. 



Owing to our ignorance of South-American Muridae it is 

 difficult to say to what species this mouse is most nearly 

 allied ; but, as ab-eady stated, it seems related to Southern 

 rather than Central American forms, and is therefore again 

 confirmatory of the view supported by Mr. Chapman as to the 

 essential difference in the origins of the faunas of the Lesser 

 and Greater Antilles. 



The specimen was marked by Mr. Smith as a " Forest 

 Rat." 



Oi'yzomys C/iapmani, sp. n. 



Oryzomi/s melanotis, Allen and Chapman, Bull. Am. Mu3. N. H. ix. 

 p. 205 (1897 J. 



The British Museum has acquired half the interesting 

 collection obtained by Mr. F. M. Chapman at Jalapa, Mexico, 

 and worked out by Allen and Chapman. Among them there 

 is a series of the Oryzomi/s termed by them 0. melanotis^ 

 Thos., and at the request of Mr. Chapman I have made a 

 careful comparison of them with the type of that species, 

 obtained by the late Dr. B idler in Jalisco. 



The two forms are undoubtedly very closely allied, but are 

 not identical, and I would therefore propose to name the Jalapa 

 form in honour of its discoverer Mr. F. M. Chapman, to whom 

 science is indebted not only for much valuable material 

 collected by him, but also for many interesting papers on his 

 own and other people's specimens. 



Size markedly smaller than in 0. melanotis, as shown 

 especially in the skull. General colour much darker, the 

 black lining on the back finer and closer and the light colour 

 less bright. Lower surface more strongly suffused with slate. 

 Ears (unfortunately for the name) even blacker than in 

 0. melanotis, the visible portion of the inner as well as of the 

 outer surface deep shining black. Wrists and ankles more or 

 less sufi'used with smoky brown. Tail as in the allied 

 species. 



Skull very similar in shape to that of 0. melanotis, but 

 much smaller; nasals narrower behind. Brain-case narrower 

 (width between most distant points of parietal ridges 10*8 to 

 11*0 millim., as against 12*1). Palatal foramina much 

 shorter and extending nearly to the level of the front of m.\ 

 Posterior narial fossa shorter. BuIUb smaller. 



Dimensions of the type (an adult female measured by 

 Mr. Chapman in the flesh) : — 



Head and body 105 millim.; tail 116; hind foot, with 

 claws, 24 ; ear 19. 



