DESCRIPTION OF GENERA AND SPECIES. 97 
series just above the white quartzite [see Blackwelder, 1907), p. 92, for general sec- 
tion giving stratigraphic relations], collected in a low bluff on the shore of T'schang- 
hsing-tau Island, east of Niang-niang-kung, Liau-tung, Manchuria, China. 
Collected by J. P. Iddings and Li San. 
In the argillaceous shales (86g) above the limestones of 35n and 35r, a few 
specimens were collected of a slender, flattened Orthotheca that is probably O.delphus. 
This form I refer to as Orthotheca cf. delphus, as the material is too poorly preserved 
for an accurate determination of its specific relations. 
Orthotheca doris Walcott. 
Plate 6, Figure 2. 
Orthotheca doris WaALcoTT, 1905, Proc. U.S. Nat. Mus., vol. xx1x, p. 21. (Described and discussed 
as a new species essentially as below.) 
Shell elongate, slender, and regularly tapering. ‘Transverse section oval or 
circular; in the type and only specimen the shell is somewhat crushed, which leaves 
the original form in doubt. The dorsal face appears to have been moderately 
convex, with rounded lateral angles that pass into the convex, rounded ventral side. 
Transverse striz and lines of growth indicate that the aperture was probably trans- 
verse. Shell apparently strong. 
Surface of shell transversely or concentrically marked by lines of growth, with 
more or less irregular striae between them; in addition there is a finely pitted surface 
between the striz, and sometimes on them, that gives a very peculiar aspect to the 
surface under a strong lens. 
The fragment representing this species has a length of 7.5 mm., with a trans- 
verse diameter at the larger end of 5 mm. 
This species is characterized by the peculiar, irregularly pitted surface. 
Formation and Locality —Middle Cambrian: (C32) A fine-grained bluish-black 
limestone bowlder believed to have come from the lower part of the Ki-sin-ling 
limestone [Blackwelder, 1907c, p. 272], collected in river drift 1 mile (1.6 km.) 
south of Chén-p’ing-hién, on the Nan-kiang River, southern Shen-si, China, 
Collected by Bailey Willis and Eliot Blackwelder. 
Orthotheca glabra Walcott. 
Plate 5, Figures 23, 23a; Plate 6, Figure 7. 
Orthotheca glabra WaLcoTT, 1911, Smithsonian Misc. Coll., vol. 57, No. 4, pp. 75-76, figs. 5 and 5a. 
(Described and discussed as a new species essentially as below.) 
Form an elongate, slender, rounded tube, with the dorsal face less convex 
than the sides and ventral face. Transverse section round, 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. 
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 com- 
munis Billings.? 
Orthotheca glabra occurs abundantly in association with Hyolithes cybele Wal- 
cott, 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 

1Tenth Ann. Rept. U. S. Geol. Survey, 1890, plate 77, figs. 3, 3a-g. 
