552 PROCEEDINGS OF THE NATIONAL MUSEUM vol. no 



albus, pedibus fuscentibus; cauda nuda longitiidine corporis; pilis 

 gastraci unicoloribus." 



Measurements, presumably taken from the dry skin are: "Korper 

 [head and body], 4" 10'" [=123 mm.] and Schwanz [tail]4" 9'" [=124 

 mm.]." These measurements do not tally with those taken in the 

 flesh by the collector (see below). Either set of measurements, how- 

 ever, lies within the range of variation for the species. Wagner 

 compared the type of concolor with the larger Hesperomys anguya 

 (= Oryzomys buccinatus Olfers) and noted that in the former the 

 color of the upperparts are much brighter, more reddish, the hair of 

 the underparts pure white, the cheeks without the gray as in anguya, 

 the feet covered with brownish hair, and the tail dark and with short 

 hairs. 



Field notes by the collector, Johann Natterer, published by Pelzeln 

 (1883) are translated from the German as follows: 



The tarsus [of the type of concolor] is much broader than that of No. 173 [Hespe- 

 romys russatus W agner = Holochilus brasiliensis Desmarest]. My dogs found it 

 in the opening of a hollow tree and I got it out with the aid of a mattock. Its 

 color is exactly like that of a reddish, white-bellied mouse from Ypanema [? 

 species]. Incisors ochraceous; ears round, gray brown, the base grayish buff, 

 toes and upperside of tarsus apparently naked and covered with small brown 

 scales on a buffy base where, on closer inspection, extremely fine short hairs 

 become visible. The hairs are somewhat longer at the roots of the claws but 

 do not extend as far as the tips of the claws. Only 6'" [13 mm.] of the base of 

 the tail is covered with fur. Total length, 10" [=261 mm.], tail 5>4" [=137 

 mm.]. 



The size, color, broad hind foot, and relatively long and thinly 

 haired tail of concolor are diagnostic of Oecomys. There is no other 

 cricetine in the upper Rio Negro region with which it can be confused. 



Specimens examined : One hundred and sixty-one, from the follow- 

 ing localities : 



Costa Rica: San Ger6nimo, San Jos6, 1 (CNHM); El General, Puntarenas, 



1 (UMMZ); Boruca, 2 (CM). 



Panama: Bugaba, Chiriquf, 2 (BM, type of tectus; USNM, 1); Barro Colorado, 

 Canal Zone, 1 (UMMZ); Cana, Darien, 11 (USNM, 9 including type of frontalis; 

 CNHM, 2). 



Colombia: Catival, C6rdoba, 1 (CNHM); Socorre, Rfo Sinii, C6rdoba, 3 

 (CNHM); Puri, Rio Cauca, Antioquia, 1 (CNHM); Muzo, Rio Minero, Boyac^, 



2 (CNHM); "W. Cundinamarca," 1 (BM, type of subluteus); Paime, Rio Minero, 

 Cundinamarca, 3 (AMNH); Pueblo Viejo, Magdalena, 5 (AMNH, 3; MCZ, 2); 

 Concepci6n, Magdalena, 1 (MCZ); Palomino, Magdalena, 1 (MCZ); Don Diego, 

 Magdalena, 8 (CM); Bonda, Magdalena, 3 (AMNH); Mamatoca, Magdalena, 1 

 (AMNH); El Llbano, Magdalena, 1 (AMNH, type of irichurus); Minca, Mag- 

 dalena, 1 (AMNH, type of mincae; Pueblo Bello, Magdalena, 3 (USNM); El 

 Salado, Magdalena, 5 (USNM); El Orinoco, Rio Cesar, Magdalena, 7 (USNM); 

 Villanueva, Magdalena, 6 (USNM); Sierra Negra, Sierra de Perija, 4 (USNM); 

 Las Marimondas, 2 (USNM); Mambita, Cundinamarca, 2 (AMNH); Medina, 

 Cundinamarca, 1 (AMNH); Buenavista, Meta 5 (AMNH); Guaicaramo, Meta, 2 



