Page:Proceedings of the United States National Museum, Volume 76.djvu/138

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A second species based on one small complete valve must be established from the Lower Cambrian Cranbrook material.

It is readily distinguished from other species by the large and numerous spines along the dorsal line and by its great width which exceeds any other species. It has four posterior marginal spines like T. polleni, but the remainder of the margin seems to be smoother. It also has short blunt spines on the keel.

Horizon and locality.—Lower Cambrian, Eager formation; (loc. 67g), near Cranbrook, British Columbia.

Holotype.—Cat. No. 80486, U.S.N.M.

Another species appears to be represented by two fragmentary valves in the red weathered shales of the Eager formation from Cranbrook. At first, owing to the large spines on the keel, it was thought that the specimens belonged to T. undosa, but a more careful comparison indicates that the differences first observed in the marginal spines actually exist and are not merely a matter of preservation. These spines are arranged in two sets, one a widely and irregularly spaced large set between which a smaller more even set occurs.

Horizon and locality.—Lower Cambrian, Eager formation; (loc. 67g), near Cranbrook, British Columbia.

Holotype.—Cat. No. 80489, U.S.N.M.

Two fine Burgess shale specimens were first regarded as representing a new genus before the manner of folding under compression and the fact that the keel is sometimes spinose were determined. The plate descriptions indicate the manner of folding in both specimens.

This species can not be confused with any other in the Burgess shale because of its scalloped frill on the keel and the marginal spines. It is much more like T. getzi from the Lower Cambrian.

Horizon and locality.—Middle Cambrian, Burgess shale; (loc. 35k) near Field, British Columbia.

Holotype and paratype.—Cat. No. 80488, U.S.N.M.

Several specimens have been secured from the Lower Cambrian in southeastern Pennsylvania and two of them represent another species