Page:Walcott Cambrian Geology and Paleontology II.djvu/268



The generic description is included with that of the type species.

Genotype.—Hurdia victoria, new species.

Stratigraphic range.—The stratigraphic range is 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.

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, British Columbia, Canada.

The generic name is derived from Hurd, the name of a mountain northeast of Leanchoil on the Canadian Pacific Railway, British Columbia, Canada.

Of this species only the valves of the carapace are known. The illustration (pl. 32. fig. 9) shows the natural size and proportion of a right valve. A larger specimen has a length of 13.5 cm.

The test was quite thin and readily compressed and distorted, which causes considerable variation in the outlines of the valve.

A faintly outlined reticulation of the surface is shown on several specimens.

The only nearly related form known to me is Hurdia triangulata.

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.

The left valve illustrating this species is slightly distorted by compression, but it outlines the average form. The largest specimen of a single valve in the collection has a length of about 10 cm. with a depth of 6 cm.

This species differs from Hurdia victoria in having a valve proportionately shorter and deeper.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, on the west slope of the ridge