Page:Walcott Cambrian Geology and Paleontology II.djvu/208

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138

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. 57

DESCRIPTION OF PLATE 20
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Pikaia gracilens Walcott				132
	Fig.	1.	(✕ 2.) A specimen flattened in shale, that shows the head, parapodia, segmentation, and outline of enteric canal. U. S. National Museum, Catalogue No. 57628.
		2.	(✕ 2.) Fragments of a portion of the body. U. S. National Museum, Catalogue No. 57629.
Oesia disjuncta Walcott				133
	Fig.	3.	(✕ 2.) Specimen showing annulations and enlarged anterior end. U. S. National Museum, Catalogue No. 57630.
		4.	(✕ 2.) Specimen with irregular sections. U. S. National Museum, Catalogue No. 57631.
		5.	Natural size. A nearly straight specimen with relatively small anterior end. U. S. National Museum, Catalogue No. 57632.

All of the specimens illustrated on this plate are from locality (35k) Middle Cambrian: dark siliceous shales in the 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, British Columbia.