NORTH AMERICAN BEAVERS, OTTERS AND FISHERS. 421 



apparently in a trap, some years previous to its final capture, but its evident health and 

 great size show that it had suffered little inconvenience from the loss of the member. 



The strong cranial and caudal affinities which this beaver shows to frondator as dis- 

 tinguished from canadensis indicate that it is more closely related to the western form. 

 In color, however, it shows a nearer approach to canadensis, as, in fact, do many other 

 animals of similar distribution and racial differences. The Mississippi and Louisiana 

 beavers are undoubtedly, from what I can hear from the furriers, the darkest and thin- 

 nest pelted of our American beavers, but their separability from what I have named 

 carolinensis is not probable. They may be considered as belonging to carolinensis rather 

 than to frondator. 



Specimens Examined. — Stokes county, North Carolina, 4. 



Sonoran Beaver. Castor canadensis frondator Mearns. 

 Plate XXI ; Fig. 2. Plate XXII ; Fig. 2. 



Castor canadensis frondator Mearns, Proc. U. S. Nat.Mus., XX, adv. sheet, Mar. 5, 1897. 



Type Locality. — San Pedro river, Sonora, Mexico, near monument No. 98, of the 

 Mexican boundary line. 



Geographic Distribution. — Southern interior of North America from Mexico to 

 Wyoming and Montana, intergrading northwardly into canadensis, southeastwardly into 

 the trans-Mississippian carolinensis and westwardly into pacificus. 



Color. — Much paler than canadensis or carolinensis. " Above russet, changing to 

 chocolate on the caudal peduncle above and to burnt sienna on the feet ; toes reddish 

 chocolate. Below grayish cinnamon, brightening to ferruginous on the under side of 

 caudal peduncle. Sides wood brown enlivened by the tawny-olive color of the over- 

 hair."* A specimen from Red Lodge, Montana (No. 32, collection of E. A. and O. 

 Bangs), taken in November, is wood brown above and below, the longer overhair of 

 upper pelage washed with pale rusty. 



Anatomical Characters. — Size large, exceeding average of Hudson bay beaver, with 

 a longer foot and broad tail. Scaly portion of tail less than twice as long as wide, hind 

 foot with claw about 185 mm. Skull massive, large, with short rostrum aud very wide, 

 short, tumid nasal bones, the average skull probably exceeding canadensis in size, cer- 

 tainly exceeding it in relative width to length and in the relative breadth of the nasals. 

 Upper molar dentition as in canadensis. 



Measurements. — Of the type: Total length, 1070 mm.; tail vertebra? from anus, 360 

 mm.; scaly portion of tail, 290 by 125 mm.; hind foot, 185 mm.; length of skull, 133 



* Quoted from Dr. Meanis' original description (I. c.) of type. 



