62 Osgood — Thirty Neiv Mice of the Genns Peromyscns. 



a fine mixture of cinnamon tipped hairs throughout; under parts white; 

 tail duslcy brownish above, white below. 



Skull.— As in typical P. grains, having the same large braincase, short 

 depressed rostrum, and relatively large audital bullae; molar teeth 

 slightlj' smaller. 



Measurements. — Average of 10 adult topotypes : Total length, 201 (194- 

 210); tail vertebrae, 111.7 (103-120); hind foot, 23.8 (23-24.5). Skull of 

 type: Greatest length, 27.2; zygomatic width, 14; nasals, 9.5; inter- 

 orbital constriction, 4.4 ; upper molar series, 4. 



Remarks. — Apparently there are two forms of the P. grains ty])e found 

 in Mexico, one very dark with dusky grayish head and cheeks, the other 

 much paler with less dusky or grayish and more ochraceous on the head 

 and cheeks. The extreme of the dark form is shown in a series fiom 

 Zamora, Michoacan. Typical gratus from Tlalpam, Mexico, is unques- 

 tionably referable to the dark form, although not so extreme as the 

 specimens from Zamora. The light form, which is therefore named, is 

 most extreme in specimens from Lagos, Jalisco. Various degrees of in- 

 tergradation are shown by specimens from a number of localities. 



Peromyscus amplus sp. nov. 



Type from Coixtlahuaca, Oaxaca, Mexico. Adult female. No. 70,158, 

 U. S. National Museum, Biological Survey Collection, November 12, 1894, 

 E. \V. Nelson and E. A. Goldman. 



Characters. — Most similar to P. felipensis, but very much i>aler; pelage 

 long and soft; color very uniform, with scarcely any dark dorsal area; 

 skull with somewhat inflated braincase. 



Color. — Type : General effect of upper parts uniform clay color produced 

 by a ground color of ochraceous buff and a fine ' peppery ' mixture of 

 dnsky ; lateral line rather broad, ochraceous buft'; forehead and orbital 

 region from posterior base of whiskers to ear grayish; anterior base of 

 whiskers buffy ; under parts creamy white with a well-developed ochrace- 

 ous buff pectoral spot ; feet white, ankles dusky ; tail white below, dusky 

 brownish above. 



Skull.— Very similar to that of felipensis, but braincase slightly higher 

 and more inflated ; anterior part of skull depressed ; audital bullfe large. 

 Measurements. — Average of 10 adult topotypes: Total length, 248 

 (235-260) ; tail vertebrae, 136 (128-145) ; hind foot, 27 (26-28). Skull of 

 type: Greatest length, 30.4; basilar length of Hensel, 23; zygomatic 

 width, 10.4; interorbital constriction, 4.5 ; interparietal, 10.4 x 3.7 ; nasals, 

 11.3; bony palate, 4.6; palatine slits, 6 x 2.3; diastema, 7.9 ; postpalatal 

 length, 10.2; upper molar series, 4.8. 



Remarks. — P. felipensis, to which amplus is related, is essentially a black 

 mouse, whereas the predominating color of amplus is ochraceous buff, 

 and except in conditions of fresh new pelage there is scarcely any black. 

 The pelage has a peculiar quality about it which baffles description, but 

 which differs to a certain extent in having less gloss or luster than in most 



