﻿76 



NORTH AMERICAN FAUNA. 



[No. 10. 



• SOREX OBSCURUS ALASCENSIS subsp. nov. 



Type from Yakutat Bay, Alaska. Type, No. 73539, 9 yg- ad., U. S. Nat. Mus., Depart- 

 ment of Agriculture coUectiou. Collected July 10, 1895, by C. P. Streator. 



General characters.—SizQ large; tail medium, about equal to body 

 without head; bind foot nearly 15 mm. Similar to /S. obscuriis, but 

 larger; similar to S. longicauda, hnt tail shorter; similar to S. fumeus 

 of the northeastern United States, but third unicuspid decidedly smaller 

 than fourth, as in most west American Shrews, and color different. 



Color. — Upper parts uniform sepia brown, finely mixed with light- 

 tipped hairs; under parts ash gray, the plumbeous showing through. 

 Tail bicolor: above, dark brown; below, whitish; tip usually dusky 

 all round. 



Cranial and dental characters. — Skull similar in size and general char- 

 acters to that of S.fumeus, from which it differs in the following points : 

 Brain case shorter, somewhat more inflated above plane of rostrum, 

 and slightly narrower; palate and postpalatal notch slightly narrower ; 

 first and second unicuspids more swollen; third much smaller than 

 fourth ; second upper true molar less deeply excavated posteriorly and 

 shorter on lingual side. The rostrum, palate, and teeth are essentially 

 the same as in fumeus^ except that the third unicus])id is smaller than 

 the fourth, as usual in western Shrews. The skull and molariform teeth 

 of Sorex alascensis are decidedly larger than those of S. ohscurus and 

 smaller than those of >S'. longicauda. Compared with S. ohscurus the 

 difference in size of cranium is due almost wholly to the great develop- 

 ment of the brain case, which in alascensis is not only larger in every 

 way but is more highly inflated above the plane of the rostrum. 



Measurements. — Type specimen: Total length, 115 mm.; tail verte- 

 brae, 45 mm.; hind foot, 14.5 mm. Average of 10 specimens from type 

 locality (Yakutat, Alaska): Total length, 116 mm.; tail vertebrse, 

 49 mm. ; hind foot, 14.8 mm. 



General remarks. — Externally Sorex alascensis resembles 8. longi- 

 cauda except that its tail is much shorter. This difference is well 

 shown in the table of measurements given under S. ohscurus (p. 73). 



The type locality of alascensis is Yakutat, Alaska; the type locality 

 of longicauda is Wrangel, Alaska. Juneau is intermediate in geo- 

 graphic position between Yakutat and Wrangel, and its Shrews of the 

 ohscurus group are, as might be expected, intermediate between alas- 

 censis and longicauda. A series of 16 specimens from Juneau differs 

 from the Yakutat series in having the tail longer (averaging 53.5 mm. 

 instead of 49.2 mm.), the ear slightly longer, the mddle upper molar 

 less emarginate posteriorly, and the color more inclining to rufous (par- 

 ticularly in No. 7 4386, in which the upper parts are much darker and 

 more rufous and the under parts strongly washed with the same color). 

 But the difference in color is probably seasonal, as a few of the speci- 

 mens which are still in summer pelage (as No. 74397) are like those 



