Page:Walcott Cambrian Geology and Paleontology II.djvu/257

 Formation and locality.—Middle Cambrian: $$\left(\tfrac{35k}{10}\right)$$ Burgess shale member of the Stephen formation (about 75 feet 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.

Carapace large, with hepatic cæca in anterior portion; eyes pedunculate. Head with 5 ? pairs of appendages. Thorax with 17 to 19 segments. Abdomen with 2 to 3 segments. Thoracic appendages leg-like, with setiferous fringes and probably gills attached to the basal joints.

One genus, Naraoia.

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

Genotype.—Naraoia compacta, 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 Narao, the name of a group of small lakes in Cataract Brook canyon, above Hector on the Canadian Pacific Railway, British Columbia, Canada.

General outline of dorsal carapace elongate oval. It is divided into two subequal parts forming the cephalic carapace and a posterior or thoracic carapace. When flattened on the shale and not distorted, the two parts are subequal in size and outline. The anterior part is distorted in figure 4, but the posterior part has nearly the natural outline of a specimen when flattened out. It has a slight inward arching at the median line where the abdomen passes from beneath it. The