1906.] Allen, Mammals from Western Mexico. 251 



having a total length (average of 4 specimens) of 3 1 . 8 and a mastoid 

 breadth of 14 mm., or exactly the same as 4 topotypes of corresponding 

 age of H. pictus. Young adult and middle-aged specimens range in 

 total length from 28.5 to 30 mm. 



The external measurements of 18 males, selected at random, are 

 as follows: Total length, 214 (205-247); tail vertebrae, 112(98-133) 

 hind foot without claws, 25.3 (24-27), to which about 2 mm. may be 

 added for the claws. Females average slightly smaller, as follows: 

 13 females, total length, 203 (197-229); tail vertebras, 105 (95-121); 

 hind foot, 24 (2227). The maximum dimensions given above indicate 

 the size of old individuals, the low general average being due to the 

 immaturity of the specimens forming the series as a whole, although 

 in no case were specimens selected which had not mature dentition. 



It thus appears that H. plantinarensis is not so very much smaller 

 than H. pictus as Dr. Merriam supposed when characterizing the form 

 from a single specimen, of which the present series are in part (practi- 

 cally all) topotypes. 



The relationship of the two forms and their distribution as repre- 

 sented by the present material have been already considered under 

 the head of H. pictus. 



28. Heteromys jaliscensis sp. nov. 



Type, No. 26325, & ad., Las Canoas, about 20 miles west of Zapotlan, 

 Jalisco, altitude 7000 feet, Aug. 6, 1905; J. H. Batty. 



Near H . canus but much darker, the upper parts being dusky gray, with a 

 slight admixture of fulvous; size smaller. 



Type, total length, 232; head and body, 120; tail vertebras, 112; hind foot 

 (from dry skin), 27.5; ear from notch, 13. Skull, total length, 32; zygomatic 

 breadth, 15. Four adult males average, total length, 228; 6 adult females 

 average, total length, 210. 



Compared with H. canus, the present species is much smaller, 

 and is further readily distinguished by its much darker coloration. 

 The skull has a relatively narrower braincase, and is nearly 2 mm. 

 shorter and much lighter and less massive. 



Represented by 4 adult males and 6 adult females from Las 

 Canoas (near Zapotlan), an adult male and female and a young female 

 from Arroyo de Gavalan, a young female from Arroyo de Plantanar, 

 and a young female from Ojo de Agua. 'The last three localities 

 are near Amatlan de Cafias, where it is apparently not common and 

 of local occurrence, as of 80 specimens of Heteromys collected at these 



