Goldman — New Mammals from North and Middle America. 113 



Montana and the upper part of the Green River Valley in northwestern 

 Colorado. It is a rather well-marked geographic race of Perodipus ordii 

 requiring close comparison only with subspecies P. o. richardsoni. The 

 species to which it belongs occupies a great area in western North 

 America from southern Washington, Idaho, and Montana southward in- 

 cluding much of the Mexican plateau region. Differentiation of the 

 various northern subspecific divisions is due to isolation and varying 

 environmental conditions on the plains and in the valleys along both the 

 eastern and western slopes of the Rocky Mountains. The material now 

 available indicates nearly every stage of intergradation between several 

 forms and the close agreement of the others inessential characters amply 

 justifies their assignment to a single species.* The range of P. o. luteolus 

 extends across to the headwaters of Green River and is approached by 

 those of P. o. columbianus, P. o. utahensis, and P. o. longipes in the 

 valleys of the western slope of the Rocky Mountains, but physical features 

 near the continental divide appear to be insurmountable barriers. 



Dasyprocta punctata nuchalis, subsp. nov. 



BLACK-NAPED AGOUTI, 



Type from Divala, Chiriqui, Panama. No. 10,081, 9 adult, Museum of 

 Comparative Zoology (Bangs collection), collected by W. W. Brown, Jr., 

 November 30, 1900. Original number 17. 



General characters. — Allied to Dasyprocta punctata isthmica and Dasy- 

 procta punctata dariensis, but strikingly different in color from either, the 

 nape distinctly blackish in contrast with shoulders, instead of nearly 

 concolor with them, and underparts much more yellowish than in the 

 other Panama forms. Pelage of back and rump without buffy basal 

 rings or bands. 



Color. — Top of head and nape strongly blackish, the nape nearly pure 

 black ; sides of neck and shoulders, anterior part of back and sides 

 coarsely mixed black and varying shades near ochraceous-buff or ochra- 

 ceous-orange (Ridgway, 1912); posterior part of back distinctly tawny, 

 paling rather abruptly to warm buff on rump ; long hairs of rump dusky 

 below buffy tips; underparts in general warm buff, this color nearly pure 

 and reaching to roots of fur on inner sides of limbs and median line of 

 abdomen, but darkened on throat, chest, and sides of abdomen where 

 the dusky basal color shows through ; feet blackish. 



Skull. — About as in D. p. isthmica and D. p. dariensis. 



Measurements. — Type: Total length, 570; tail vertebrse, 20; hind foot, 



* Perodipus ordii will therefore stand subspecifically as follows: 



Perodipus ordii ordii (Woodhouse) El Paso, Texas. 



Perodipus ordii columbianus Merriam Umatilla, Oregon. 



Perodipus ordii utahensis Merriam Ogden, Utah. 



Perodipus ordii chapmani (Mearns) Fort Verde, Arizona. 



Perodipus ordii montanus (Baird) Fort Garland, Colorado. 



Perodipus ordii longipes Merriam Echo Cliffs, Arizona. 



Perodipus ordii luteolus Goldman Casper, Wyoming. 



Perodipus ordii richardsoni (Allen) Beaver River, Oklahoma, 



Perodipus ordii palmeri (Allen) San Luis Potosi, Mexico. 



