Page:Walcott Cambrian Geology and Paleontology II.djvu/271

 The numerous small appendages projecting outside of the carapace on the lower side indicate that the body had many segments and appendages, but with only one specimen for study I shall not attempt at this time to discuss it, as it is possible that other specimens will be discovered during the field season of 1912.

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 generic description is included with that of the type species.

Genotype.—Carnarvonia venosa, new species.

Stratigraphic range.—The stratigraphic range is limited to a band of gray, buff-weathering siliceous shale forming the upper 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 Carnarvonia, is derived from Carnarvon, the name of a mountain of the President Range, northwest of Field, British Columbia, Canada.

The figure on plate 33, of the two valves united and pressed flat on the shale, illustrates all that is known of this genus and species. The size and proportions are shown by the figure.

The reticulated surface, adductor muscle scars, and vascular markings on the shell are beautifully shown on the specimen and in this illustration.

Formation and locality.—Middle Cambrian: $$\left(\tfrac{35k}{10}\right)$$ Burgess shale member of the Stephen formation (about 75 feet (22.8 m.) above the phyllopod bed near the base of the shale), 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.