26 



KOETH AMEEICAIT FAUKA. 



[No. 40. 



before May 10 are still in the old winter coat, with little evidence of 

 molt. Skins collected from May 20 to June 1 have renewed over 

 most of the underparts and somewhat on the head and shoulders. 

 Numerous examples taken from June 1 to 10 are all in fresh coat 

 except on the lower rump and tail. Skins collected July 15 to 30 are 

 in full summer coat. By August 10 there is much evidence of wear 

 over the forward haK of body^, and by early September the f aU renewal 

 has commenced. As in the case of C. ludovicianus, this progresses 

 forward, and by September 25 to October 1 is complete. 



SlcuTl.—LsLTgeT than in C. parvidens or C. gunnisoni; otherwise 

 much like skuU of parvidens but with narrower interorbital region. 

 Differs further from skull of gunnisoni in the less broadly spreading 

 maxillary arm of zygoma, large and flat mastoids, larger audital 

 buUse, and less rounded inferior rim of angle of ascending branch 

 of jugal; occiput viewed from behind broader and flatter. 



Measurements. — Averages of 13 adult males from Wyoming: Total 

 length, 358 (340-370) ; tail vertebrae, 57 (44-60) ; hind foot, 62 (60-65). 

 SlcuU: Condylobasal length, 58.7 (56-61.3); zygomatic breadth, 43.8 

 (41.7-45.4); mastoid breadth, 29 (27.4-30); length of nasals, 22 

 (20.7-23.1); length of mandible, 43.1 (41.6-44.9); maxiUary tooth 

 row, alveoli, 15.7 (15.1-16). For detailed measurements of speci- 

 mens see page 35. 



Type specimen. — No. 186472, U. S. National Museum. Adult 

 female, skin and skull (teeth moderately worn). Collected Septem- 

 ber 15, 1888, by Vernon Bailey; original number 224 (Merriam 

 collection, skin 4668, skuU 5319). In worn summer coat anteriorly 

 and in fresh winter coat posteriorly. 



Remarks. — In 1898, Dr. J. A. Allen ^ proposed that the name 

 Arctomys lewisii of Audubon and Bachman be revived for this species. 

 The specimen on which Arctomys lewisii was founded was recorded as 

 No. 461 of the Zoological Society of London coUection. In reply to 

 my inquiry as to the possible existence of this type specimen in the 

 British Museum, Mr. Oldfield Thomas wrote, under date of January 

 6, 1915, that the specimen is stiU preserved, is numbered 55.12.24.144 

 of the Museum register, but that it is a species of Marmota, and not of 

 Cynomys as supposed by Dr. Allen. 



The ranges of Cynomys leucurus and C. gunnisoni are not known 

 actually to meet, but the ranges of C. leucurus and C. ludovicianus 

 do meet, and for a short distance overlap, at several points in Montana 

 and Wyoming. Both species are constantly enlarging their ranges, 

 pushing out into new valleys, and consequently frequently find 

 themselves in close proximity. Individuals of one species sometimes 

 wander into villages of the other. In the Bighorn Basin, in Montana, 

 Bailey found the species living in close proximity but always apart. 



1 Bull. Amer. Mus. Nat. Hist., X, p. 456, 1898. 



