Page:Walcott Cambrian Geology and Paleontology II.djvu/132

76 except for the slightly flattened dorsal side. Operculum unknown. Shell rather thick, and with a smooth surface.

The largest specimen in the collection has a length of 5 mm.

Observations.—This species is distinguished from other Chinese forms by its rounded tube and smooth surface. It is the representative in form of the American Orthotheca communis Billings.

Orthotheca glabra occurs abundantly in association with Hyolithes cybelc Walcott, in the Dorypyge richthofeni zone of Manchuria. Some of the shells have a long, slender terminal section to the tube that is more or less slightly curved. It is so slender and round that it suggests the tube of Hyolithellus.

Formation and locality.—Middle Cambrian: (C71) massive cliff making limestone in the central portion of the Ki-chóu formation, 4 miles (6.4 km.) southwest of Tung-yü ; and (C72) thin green gray limestone interbedded with ocherous and green clay shales, overlying the massive oolite in the Ki-chóu formation, 4 miles (6.4 km.) east of Fang-lan-chön ; both in Shan-si, China.

Collected by Eliot Blackwelder.

Also (35n) Middle Cambrian: Fu-chóu series; limestones near the base of the series just above the white quartzite, collected in a low bluff on the shore of Tschang-hsing-tau island, east of Niang-niang-kung, Liau-tung, Manchuria, China.

Collected by J. P. Iddings and Li San.

Of this form only one fragment of the pygidium was found in the collection from Manchuria. This is so characteristic that I do not hesitate to identify it as the pygidium of an Albertella although stratigraphically it occurs at a higher horizon in the Middle Cambrian than the American species of the genus.

A pygidium illustrated by M. Barrande as Paradoxides desideratus Barrande may possibly belong to a species of Albertella. The axial lobe of the pygidium has seven rings and a terminal section and the pleural lobes have lateral spines.

Formation and locality.—Middle Cambrian: (36f) Fu-chóu series; about 1000 feet (305 m.) above the white quartzite, collected in a