452 CONTRIBUTIONS TO A REVISION OF THE 
Geographic Distribution.—Arid southern interior of North America, from Mexico, 
probably to Wyoming. 
Color.—Of type, fide Mearns, J. c.: “ Above dark brown, without reddish tinge ; this 
color changing gradually to a light grayish brown below, being palest (almost whitish) 
upon the sides of the head below the level of the eyes and upon the under side of the 
head and neck as far back as the fore limbs. . . . . The long hairs of the lighter por- 
tions of the body are pointed with yellowish gray and upon the upper surface of the 
head and neck the tips of the hairs are yellowish brown, giving a paler cast to that part 
of the dorsum.” 
Anatomical Characters.—Size, large, with a very long hind foot, the body length 
measurements exceeding those of any other specimen of North American otter exam- 
ined or recorded.* Webs of feet not densely haired beneath. Hind foot, 145 mm. Total 
length reaching 1300 mm. Skull—size, large, nearly as great as in largest Alaskan 
pacifica, but small for the great relative length of body, “less massive, broader, with 
more evenly rounded zygomatic arches and with the brain case more convex or bulging 
in its outlines.” ‘‘ Arizona skulls differ from all others in the slender, attenuated postor- 
bital processes and in the greater height of the lower jaw from angle to condyle, or to 
summit of coronoid process. From its geographically near neighbor, L. felina of Cen- 
tral America, it presents many cranial and dental differences; in fact, skulls of the lat- 
ter are so very distinct [in their inferior concavity, frontal depression, short muzzle, 
narrow postorbital constriction and absence of the heel in front of the antero-internal 
cusp of the last upper molar] from any known specimens from North America, north of 
Mexico, as to be distinguishable from them at a glance.” 
Measurements.—Of type: “Total length, 1300 mm.; head and body (measured from 
tip of nose to anus), 815 mm.; tail measured from anus to end of vertebrae, 472 mm. 
. ear, height above crown, 15 mm.” No skull measurements given. 
Remarks.—I have accepted Dr. Mearns’ very full and satisfactory diagnosis of the 
Arizona otter, given in the Bulletin of the American Museum of Natural History, as 
conclusive eyidence of the existence of a recognizable race in arid interior America, 
south of Montana. Its great size and light color together form a combination not found 
in any other known or named otter. 
It has been thought unnecessary to examine the type, as, owing to the author’s 
remoyal from Philadelphia during the completion of this paper, such an examination 
would have caused a greater risk to the type specimens than the facts warranted. 
* The great size of the type, as compared with an adult male also recorded by Dr. Mearns from Arizona, indicates 
that the sex of the type may have been wrongly determined. If correct, the size to be expected of a full-grown male 
sonora would be extraordinary. 
