188 U. Ss. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
There is apparently a preponderance of the light tips to the long hairs along the middle of 
the back and on the sides of the tail. . 
The concealed under fur is liver brown at the tip; that on the belly and sides being yellowish 
white at the base, the amount and clearness of the white decreasing to the median line of the 
back. 
A comparison of this specimen with a very fine ZL. canadensis, killed in the Potomac river, 
near Washington, presents the following differences : 
The naked muzzle is decidedly shorter antero-posteriorly, the width remaining the same. 
Length of the naked portion is less than its width, instead of being greater, as in the J. 
canadensis. The angle of the posterior outline is consequently less acute and is shorter, not 
running so far back on the forehead. The septum of the nostrils is narrower, and there is no 
naked point running down from its middle line and partly bisecting the middle of the upper 
lip, as in L. canadensis. 
There is much less hair on the under surfaces of the feet. The peninsula of hair extending 
forward over the naked portion of the sole in L. canadensis is wanting entirely, and there is 
but little hair on the web between the fingers. The first, fourth, and fifth fingers are entirely 
naked under their middle line, instead of having the balls isolated by hair from the naked palm.* 
A nearly similar condition prevails in the hind feet, except that there is no hair on the middle 
line of the inferior surface of any of the toes. 
How far the characters thus adduced are sufficient to establish differences in species can only 
be determined by a comparison of more specimens. All the eastern skins of otters I have seen 
agree pretty well with the above description of L. canadensis, the hair on the under surface of 
the feet being distinctly appreciable when the digits are approximated, which is not the case in 
the California specimen. As a species has been instituted by Gray, I shall adopt it, whatever 
hesitation I might feel at introducing a new name based on a single specimen. 
A comparison of the skull of the California otter with that ot eastern specimens exhibits very 
close affinities, both being distinguished from the European L. vulgaris by common character- 
istics of great development of post orbital process of frontal bone, broad interorbital space, very 
broad and short muzzle, &c. 
List of specimens. 
Measurements. 
Catalogue | Correspond’ g Locality. When Whence obtained. |Natureoff Collected by— 
. ale 7 . a 20) ? 
number. | No. of skull. collected, specim’D | 1 oot | Tail. 
of tail. | 
1191 2029 Cascade Mts., O. | Sept., 1855 | Lt. R.S.Williamson.| Skin---| 33.00 | 19.00 | Dr. J.8. New- 
T., lat. 44°, 160 ‘ berry. 
miles south of 
the Columbia. 
