Page:Walcott Cambrian Geology and Paleontology II.djvu/186

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A small slender species not over 20 mm. in length. The setæ are irregular in size and appearance and suggest partially worn macerated specimens of the slender forms of C. setigera.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, on the west slope of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field, British Columbia.

Polychætous annelids with a slender, straight, or slightly curved tube. Probably chitinous. A number of tubes of Selkirkia major show the animal projecting from the end as illustrated by fig. 6, pl. 19. It is divided into segments or sections and more or less provided with short spines at the base of the anterior or end section. A number of short-jointed appendages indicate a rather large head.

Genotype.—Selkirkia major (Walcott).

Two other species S. fragilis and S. gracilis are referred to this genus on account of the form of the tubes; they are clearly not to be referred to Hyolithes.

Stratigraphic range.—The stratigraphic range in limited to a band of dark siliceous shale about 4 feet in thickness forming a part of the Burgess shale member of the Stephen formation at locality (35k) near Burgess Pass, and on the slope of Mount Stephen it was found extending through 50 feet or more of the coarse siliceous shales.

Geographic distribution.—On the slope of the ridge between Wapta Peak and Mount Field, north of Burgess Pass, and about 3800 feet above Field on the line of the Canadian Pacific Railway; and on the slope of Mount Stephen 2300 feet above Field; both in British Columbia, Canada.

Generic name derived from Selkirk, name of mountain range, British Columbia, Canada.

Orthotheca major, 1908, Canadian Alpine Journal, Vol. 1, p. 246, pl. 1, fig. 11.

This species was founded on a long, slender, delicate tube that is known only as it occurs flattened on the surface of the shale. The apical end is broken off on all the specimens in the collection. The