Page:Walcott Cambrian Geology and Paleontology II.djvu/188

122 discussion of the subject by Dr. G. F. Matthew, who concludes that Hyolithes and allied forms should be classed with the annelids, along with Hyolithellus and other slender tubes.

During the field season of 1911 we hope to add something more to the information about the animal of Selkirkia.

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; and (14s) about 2300 feet (701 m.) above the Lower Cambrian and 2700 feet (823 m.) below the Upper Cambrian, in the Ogygopsis zone of the Stephen formation, at the great "fossil bed" on the northwest slope of Mount Stephen, above Field on the Canadian Pacific Railway; both in British Columbia, Canada.

A thin tube that when flattened has a diameter at the larger end of from 2.5 to 3 times its length; the slender proximal end is curved. The largest specimen has a length of 25 mm. This species differs from Selkirkia gracilis (fig. 9), and S. major (fig. 6) in its greater proportional diameter at the aperture.

Formation and locality.—Middle Cambrian: (14s) about 2300 feet (701 m.) above the Lower Cambrian and 2700 feet (823 m.) below the Upper Cambrian, in the Ogygopsis zone of the Stephen formation, at the great "fossil bed" on the northwest slope of Mount Stephen, above Field on the Canadian Pacific Railway, British Columbia, Canada.

A number of fine specimens of this species have been found in the same layers of shale with S. major, but unfortunately none of them show any traces of the animal. The tube is very thin and, unlike S. major, retains the slender, more or less curved proximal end. A comparison of fig. 9 with figs. 6 and 8 shows how this flattened tube differs in form from S. major and S. fragilis.

The largest tube has a length of 47 mm. and a width of 10 mm. at the aperture.