( 41 ) 



But it must be confessed that though essentially Oryzomys in tooth structure, 

 the yhoeopus-chvysomelas group are very aberrant, as compared with normal 

 Uryzomys, and I would suggest that a special subgenus should be formed for their 

 reception. This might be called Melanomys from the general dark colour of its 

 members, and its characteristics would be the short tail and generally Akodont 

 external form of the species, the strictly Oryzomyine molars, the broad-rounded 

 brain-case, short muzzle and well-marked supra-orbital ridges. The type would be 

 Oryzomys {Melanomys) phoeopus Thos. from Ecuador, to which 0. (M.) chrysomelas 

 is nearly allied. 



14. Reithrodontomys sp. 

 Oebaco, '2. 

 (Too young for determination.) 



15. Sigmodon sp. 

 Cebaco, 8 (mostly young). 



16. Proechimys centralis chiriquinus Thos. 

 Gobernador, 15; Brava, 2; Cebaco, 13. 



17. Coendou rothschildi * Thos. 



Sevilla, 5 ; Brava, 1 . 



Allied to G. qwichua, Thos., of Ecuador, but more strongly wliite speckled, and 

 with various cranial differences. No relationship to the common Central American 

 form G. viexicanua. 



Size slightly larger than in G. qwichua. . Pelage practically entirely spinous, a 

 few short fine hairs mixed with the spines, but these are only visible on close exami- 

 nation. General colour black, coarsely and numerously speckled with white; rump 

 black. Individual spines of back about 40 — 50 mm. in length, the basal three-fifths 

 yellowish white, the next two-fifths black or blackish brown, the tips white or (rarely) 

 bro\niish white. In skins in good condition the basal white scarcely shows through, 

 being hidden by the dark subterminal rings of the spines. Spines of rump shorter 

 than those of body, without the white tips, and with less or no basal white. Fine 

 hairs of muzzle black. Head grizzled black and white, like body. Ears with a small 

 tuft of bristles, mostly white, but some with dark Ijases. Under surface clothed with 

 spinous bristles, arranged in tufts of three or four together, white basally, brown 

 -mesially, and the tips white. Upper surface of hands and feet dark brown. Tail 

 with the upperside of its base coloured and spinous like the rump ; sides of base 

 white, grizzled like tlie Ijody generally ; rest of tail (except the tip) uniformly black, 

 clotlied with thick coarse black bristles, tip practically naked. 



Skull rather larger than that of G. quichua, very variable in shape, as usual in 

 this group. Dorsal outline more iuHated above the orbits than above the squamosals, 

 the converse being the case in G. quiclma; supra-orbital and parietal ridges well 

 defined. Nasal oi)ening larger, and, especially, wider than in G. quichua. jMuzzle 

 rather more. thrown fijrward, the incisors pointing less directly downwards. Palatal 

 foramina long and wiile, but in no two specimens alike. Anterior cheek-tooth (p*) 

 scarcely (jr not laiger than the molars. 



' I'lL-liiuiniuy ilctciiptiuii, .Inn. Ma;/. N. U. (7). a. p. lOH. 19U2. 



