Page:Walcott Cambrian Geology and Paleontology II.djvu/195

NO. 5 minute hooks arranged in five or six concentric rings (figs. 1, 2, 4, and 5). At the posterior end there is a concentric row of stronger hooks as shown by figs. 1 and 3.

The proboscis is strong, retractile, and papillose. In fig. 4 it is extended nearly to its full length; in figs. 1 and 5 partially contracted, and in fig. 2 apparently broken off.

There are no traces of parapodia or openings on the surface except at the ends of the body.

Enteric canal small and extending the entire length of the body from the mouth to the posterior end (fig. 2). The mouth is at the base of the proboscis in front of the bands of hooks (fig. 2). The anus appears to have been at the posterior end, as indicated by the termination of the enteric canal in figs. 1 and 2.

The average length of adult specimens is from 8 to 10 cm. One 9 cm. in length is 2 cm. across its widest part as it is flattened in the shale. Other specimens are more contracted, shorter, and proportionally broader (fig. 1).

Observations.—There is a large series of this species in various conditions of preservation. Some show the annular lines and bands with great distinctness (figs. 1 and 3) and others are apparently smooth (fig. 2). The proboscis may be protruded (fig. 4), partially pushed out (fig. 5), or absent (fig. 2). Bands of longitudinal muscles are suggested by the lines near the inner curve of fig. 1, and concentric muscles by the annular bands.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, west slope of ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field on the Canadian Pacific Railway, British Columbia, Canada.

This species dififers from Ottoia prolifica in its proportionally more slender form when elongated (fig. 5), and straighter outline both when elongated and contracted (fig. 6). The hooks are also much finer and extend farther back on the anterior end. The annular lines and interspaces are also finer and more irregular.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, west slope of ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field on the Canadian Pacific Railway, British Columbia, Canada.