Page:Walcott Cambrian Geology and Paleontology II.djvu/184

118 One genus, Canadia.

Observations.—For comparison with recent annelids we turn to the Aphroditidæ, Amphinomidæ, and Palmyridæ, but in none of these do we find the slender body, narrow segments combined with the small parapodia, and great development of setæ without, scales on the dorsal surface.

The description and illustrations of Canadia spinosa will serve to indicate this genus. The other species express, in variations in size and position of the bundles of setæ, characters that for this preliminary study are considered to be of specific value.

Genotype.—Canadia spinosa, 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.

Observations.—Five species are referred to Canadia: C. spinosa, C. setigera, C. sparsa, C. dubia, and C. irregularis. Of these the first two are illustrated on pl. 23. The other three species will be illustrated in a final paper on this fauna.

Generic name derived from Canada.

Body slender, formed of 20 to 21 segments that, when flattened on the shale, are a little longer than wide; each segment has a pair of parapodia with a dorsal and ventral bundle of strong non-jointed setæ. The setæ are finely illustrated by figs. 4, 6, and 7. Head minute, with a pair of large tentacles curving outward from the front anterior margins; a bundle of fine setæ occurs on each side of the head back of the base of the large tentacles. A straight slender enteric canal is indicated on several specimens. Mouth and anus not seen, but probably at or near the end of the annelid.

Dimensions.—The largest adult specimen has a length of 34 mm., with a width of the body at the seventh segment from the head of 1.5 mm.