240 Bulletin American Museum of Natural History. [Vol. V.] 



4.3 ; length of nasals, 8 ; interparietal, length, 2 ; interparietal, breadth, 8.4 ; 

 incisors to first premolar, 2.5 ; length of upper molar series, 3 ; length of lower 

 jaw, 11.7 ; height of same at condyle, 4.3. 



Type, ? ad., El General, altitude 2150 feet, Feb., 1891, coll. H. Pittier. 



This species is based on four specimens, all nearly or quite 

 adult (in one the teeth are well-worn), three of them taken on 

 ^1 General at an altitude of 2150 feet, and one in the Cerro de 

 Buena Vista, " altitude 10,342 feet," in February, 1891, by H. 

 Pettier. Another specimen, labeled " La Carpintera, $ , July 26, 

 1891, Geo. K. Cherrie," I also refer to the same species. This 

 would seem to give the species quite a range in altitude, if the 

 elevation recorded on the labels is correctly indicated. These 

 are all skins, four of which are accompanied by their separate 

 skulls. 



Oryzomys costaricensis needs comparison with no other species 

 described from north of the Isthmus of Panama. It is well 

 characterized by its very small size (head and body three inches 

 or less) and its exceedingly long tail (nearly five inches). In 

 size, coloration and general external appearance it is strongly 

 suggestive of a very long-tailed species of Reithrodontomys^ but 

 the resemblance is entirely superficial. Its nearest representative 

 appears to be Oryzomys lon&icaudatus (Benn.), of Chili and Peru, 

 from which, however, it is obviously distinguished by its small 

 ears and different coloration. The absence of the usual supra- 

 orbital ' bead ' may be easily due to the very small size and con- 

 sequent delicate structure of the species. 



*l6. Oryzomys couesi Alston. One specimen, female, 

 Bahia de Salinas (on the Pacific coast), July, 1890, A. Alfaro. 

 Skin and skull, from an alcoholic specimen, with the following 

 measurements inscribed on the label: "Length, 9.15 in. [232 

 mm.] ; tail, 5.35 [135.6] ; hind foot, 1.17 [29.7]." This specimen 

 is provisionally referred to O. couesi Alston, as recently redefined 

 by Thomas (Ann. and Mag., 6th Ser., XI, 1893, p. 403). 



17. LepUS gabbi Allen. One specimen, San Jose. 



18. Didelphis (Micoureus) murina Linn. One specimen, 

 a half-grown male, Jimenez, August, 1891, A. Alfaro. 



