1916.] 



CYXOMYS LUDOVICIANUS LUDOVICIANUS. 



17 



62 (61-83). SluU: Condylobasal length, 59.8 (57.2-62.6); zygomatic 

 breadth, 45 (42.9-48.1); mastoid breadth, 28.5 (27.5-31); length of 

 nasals, 23.8 (22-25); length of mandible, 45.9 (43-49.4); maxillary 

 tooth row, alveoli, 16.6 (16-17.5). Females average very slightly 

 smaller than males, but the difference in size is, as a rule, barely per- 

 ceptible. For detailed measurements of specimens, see page 34. 



Weiglit. — The weights of adult examples of C. I. ludovicianus are 

 recorded in collectors' field catalogues as follows: Alma, Nebraska, 

 October 21, c?, 3 lbs., 9, 2 lbs. 4 oz.; Tilyou's Ranch, Montana, 

 October 1, $ , 2 lbs. 3 oz. 



Type specimen. — Ord's description of this prairie-dog was drawn 

 from a stuffed skin in Peale's Museum, Philadelphia, supple- 

 mented by notes from the narrative of Lewis and Clark. This 

 specimen was without doubt the identical skin which later on was 

 more fully described by Say.^ It has long since been lost sight of. 



Remarks. — As explained in the account of the pelage changes, there 

 is considerable seasonal color variation in the common prairie-dog, 

 but a comparison of specimens in exactly the same state of pelage 

 from all parts of the animal's range proves the absence of any con- 

 stant geographical differences. There is likewise a remarkable 

 uniformity in size, the averages and extremes of long series from 

 northern States being virtually identical with measurements of 

 specimens from Texas. The alleged form from Oklahoma, described 

 by Dr. Elliot as Cynomys pyrrotricTius, is not subspecifically distin- 

 guishable from C. I. ludovicianus. Specimens from this region are 

 commonly stained by the red soil, and sometimes so naturally as 

 almost to defy detection as a stain. Numerous examples, however, 

 show the telltale red soil on the toes and feet, and a careful micro- 

 scopic examination of the hairs often shows the particles composing 

 the stain, which can be perceptibly lightened by a moment's washing 

 with alcohol or benzine. There are, furthermore, absolutely nor- 

 mally colored specimens from various parts of the area included in 

 the distribution of the ''red-haired" prairie-dogs, and all the young 

 specimens are indistinguishable from juvenile examples from the 

 Dakotas and other parts of the range of the species. Reddish skins, 

 in all respects like the specimens of "pyrrotricJius'^ from Oklahoma, 

 are not infrequently found in other parts of the prairie-dog's range 

 where soil conditions are favorable for producing such a stain. 



On the basis of skull characters the subspecies ludovicianus is typ- 

 ical over the northern parts of its general distribution, in Montana, 

 the Dakotas, and Wyoming. The ''area of intergradation " with C. I, 



1 See Guthrie's Geog., 2d Amer. ed., p. 303, under "Columbia Marmot," where Ord states that "A stuffed 

 skin of the Louisiana Marmot is in the Museum of Mr. Peale." Also, Say, in Long's Exped. to Rocky Mts.^ 

 I, p. 452, 1823. 



20651°— 16 2 



