250 Bulletin American Museum of Natural History. [Vol. XXII, 



It is remarkable that the only positive character that will readily 

 distinguish these three forms is the squarely truncated nasals in 

 pictus and the distinctly emarginate nasals in plantinarensis and 

 escuinapa, all of which forms probably intergrade geographically. 

 If the decided difference in the form of the posterior border of the 

 nasals, in the absence of any other appreciable differences of size, 

 form, number of toe-pads, or coloration, be considered of specific 

 importance, then pictus will stand as a species, and plantinarensis 

 also as a species with escuinapce as a subspecies of the latter. 



None of these 13 specimens are very old, being mostly young 

 adults, and thus fall below true pictus in size, averaging practically 

 the same as the plantinarensis specimens of corresponding age. 



These two forms, as represented in the present series, are almost 

 separated geographically, all of the specimens from the Wakenakili 

 Mountains, Rio Santa Maria, and Sal se Puerdes, 15 in number, 

 being true pictus, while all those from Ojo de Agua, Palo Amarillo, 

 and Amatlan, 25 in number, are true plantinarensis; but of n speci- 

 mens from Estancia, Jalisco, and 5 from Arroyo de Plantanar, one of 

 the former and two of the latter, or 3 specimens out of 16, are true 

 plantinarensis while the others are pictus. In about 3 skulls out 

 of 53 the form of the posterior border of the nasals is irregular, being 

 convex rather than truncate. 



27. Heteromys pictus plantinarensis Merriam. 



Forty specimens, collected as follows: Amatlan de Canas and 

 vicinity including the localities Ojo de Agua, Palo Amarillo, Estancia, 

 Rio Ameca, Arroyo de Plantanar, etc. (local names not on maps, 

 on the boundary between Tepic and Jalisco), Jan. 14 to Feb. 28. 

 The various localities, some of them in Tepic and some in Jalisco, 

 are represented as follows: Rancho Palo Amarillo, Tepic, 13 speci- 

 mens, Jan. 2-4 and 13-16; Amatlan, Tepic, 9 specimens, Jan. 4-11; 

 Estancia, Jalisco, 10 specimens, Jan. 23-31 and Feb. i, 3, 6, 22, and 

 28; Ojo de Agua, Tepic, 3 specimens, Feb. 9, 14, and 16; Arroyo de 

 Plantanar, Jalisco, 5 specimens, Feb. 18-20; Volcan de Fuego, i speci- 

 men, July 13. (This last specimen has no skull, and its reference 

 here is thus necessarily provisional.) 



Of these 40 specimens only 3 or 4 are very old, with worn teeth, 

 the greater part being middle-aged or young adults, with a few 

 still younger. Taking the skulls as a basis for comparison, the older 

 specimens are as large as topotypes of corresponding age of H. pictus, 



