Range.—Vancouver Island from Sayward south, and Bowen Island.

Diagnosis.—Size small for the species; average and extreme measurements of 6 specimens from Alberni Valley, Vancouver Island, are: total length, 106.5 (97-115); tail, 41.7 (40-43); hind foot, 12 (11-13) (Jackson, 1928:107). Ventral parts brownish, winter pelage reddish brown rather than grayish.

Comparisons.—Differs from S. v. vagrans in more brownish ventral parts and more brownish, rather than grayish, winter pelage; differs from the sympatric S. v. isolatus in shorter tail, shorter hind foot, more narrow skull, and smaller teeth.

Remarks.—This is a poorly differentiated subspecies which is closely related to S. v. vagrans. The differences in color noted are average ones. Some individuals of this shrew might be difficult to separate from S. v. isolatus. The slight degree of morphological divergence is such that intergrades might be expected to occur. Possibly some habitat separation occurs, but such has not been reported.

Specimens examined.—Total number, 3. British Columbia: Vancouver Island: Mt. Washington, 1 KU; Nanaimo, 1 BS; type locality, 1 BS.

Marginal records.—British Columbia: Sayward (Anderson, 1947:18); Bowen Island (Hall, 1938:463); Alberni (Jackson, 1928:107).

CONCLUSIONS

1.Sorex vagrans, S. obscurus, S. pacificus, and S. yaquinae are conspecific with one another. Each is a valid subspecies but all should bear the specific name Sorex vagrans Baird, 1858.
2.The subspecies of Sorex vagrans form a cline from large (pacificus) to small (vagrans). The cline is bent in such a manner that the terminal subspecies occur together. Where the two subspecies occur together, individuals of one subspecies do not crossbreed with individuals of the other subspecies and therefore react toward one another as do full species. Sorex vagrans vagrans occurs sympatrically with S. v. sonomae, S. v. pacificus, S. v. yaquinae, S. v. bairdi, S. v. permiliensis, and S. v. setosus. S. v. vancouverensis occurs sympatrically with S. v. isolatus.
3.The sympatric existence of the terminal subspecies of the Sorex vagrans rassenkreis is made possible by marked differences between them in size and in ecological preference.
4.The west-coast subspecies, sonomae, pacificus, yaquinae, bairdi, and permiliensis probably differentiated from the Great Basin and Rocky Mountain subspecies, vagrans, obscurus and monticola, during a separation caused first by aridity in the Great Basin, and secondly by glaciation of the Cascade Mountains and the Sierra Nevada, possibly in the Sangamonian and Wisconsinan ages respectively.
5.Sorex v. vagrans originated in the Great Basin and arrived on the Pacific Coast after the last deglaciation of the Cascades and Sierra Nevada.
6.In S. vagrans, heterogonic growth is illustrated; the larger the skull, the larger the rostrum in proportion to the skull as a whole.
7.In the species S. vagrans, size and color vary geographically more than do other features.
8.The S. ornatus group, S. longirostris, and S. veraepacis had a common ancestor with S. vagrans, possibly in the Illinoian Age.
9.S. vagrans, the S. ornatus group, S. veraepacis, S. longirostris, S. palustris, S. bendiri, and the S. cinereus group, because of structural resemblances, should be placed in a single subgenus, Otisorex. S. trowbridgii, the S. arcticus group, the S. saussurei group, S. merriami, S. fumeus, and S. dispar, should be included in the subgenus Sorex.
10.Sorex cinereus occurs with the medium-sized and large-sized S. vagrans in the Rocky Mountains and in Canada, but does not occur with the smaller subspecies of S. vagrans, probably because competition between two shrews of like size excludes S. cinereus.

Table 1—Cranial Measurements of Sorex vagrans