Page:Walcott Cambrian Geology and Paleontology II.djvu/95



Body elongate, cylindrical, and contracting at each end. Marked by from eight to ten longitudinal bands that are outlined by narrow, slightly elevated lines as shown in fig. 3, pl. 13. The anterior end has a ring of what appear to be narrow plates surrounding a central opening. The interpretation of the ring is that it formerly surrounded the œsophagus near its outer end and that the outer margin of the œsophagus with the tentacles has been removed. The posterior end is contracted slightly. No trace of the anal opening has been seen.

Surface smooth so far as determined.

Two specimens have been found and photographs of both are reproduced (natural size) by figs. 2 and 3, pl. 13.

As mentioned under the genus, the body of this species has the general form of the body of Synaptula hydriformis (Lesseur).

No traces of calcareous deposits have been observed, except possibly in the ring about the anterior end. In this the calcareous matter, if it was originally present, has been removed. My present impression is that nearly all calcareous matter was removed by solution in the mud deposit prior to its consolidation and alteration into rock.

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

All that is known of this genus is given under the description of the species P. nathorsti.

The relation of the genus to the Order Rhizostomæ is shown by its

(a) Discoidal bell without known annular furrow or pedalia,

(b) Margin of bell cleft into lappets,

(c) Absence of tentacles, and

(d) Mouth probably with adradial arm-like processes.