96 RESEARCH IN CHINA. 
Shell elongate, slender, tapering gradually to an acute point. Transverse sec- 
tion subcircular, slightly flattened on the dorsal side. Ventral face strongly and reg- 
ularly convex transversely; the dorsal and ventral faces meet to form the rounded 
lateral angles of the shell, the dorsal face being narrow and slightly flattened. 
Aperture transverse, as indicated by the transverse lines of growth. 
Surface of the shell smooth and polished, with only a few very obscure traces 
of transverse concentric lines of growth. 
A specimen 13 mm. long has a diameter of 4 mm. at the larger and 1.75 
mm. at the smaller end; on the side, 2 mm. and 1 mm. 
This species resembles, in its slender tube and nearly circular section, Hyolithes 
communis Billings [Walcott, 1891a, plate 77, figs. 3, 3a-g]. It may be com- 
pared with Orthotheca stylus Holm [1893, p. 52, plate 1, figs. 16-20; plate 6, figs. 6-9], 
except that it does not have the curvature of that species nor the cancellated surface. 
Its slender tube and nearly circular section are much like those of Orthotheca tere- 
tiusculus Linnarsson as illustrated by Holm in his memoir on Hyolithide [1893, p. 
51, plate 1, figs. 21-24]. 
Formation and Locality —Middle Cambrian: (C23) Upper part of thin-bedded, 
gray oolitic limestone at the base of the Ch’ang-hia formation [Blackwelder, 1907a, 
p.32 (second list of fossils), and fig. 6 (bed 20), p. 25], 50 feet (15 m.) below the base 
of the cliffs 1 mile (1.6 km.) east-southeast of Ch’ang-hia, Shan-tung, China. 
Collected by Eliot Blackwelder. 
Orthotheca delphus Walcott. 
Plate 6, Figures 1, 1a-0, 5, 6. 
Orthotheca delphus WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xx1x, p. 20. (Described and discussed 
as a new species essentially as below.) 
Shell straight, elongate, slender, tapering gradually to an acute point. Trans- 
verse section subelliptical, with the dorsal side flattened. Dorsal face gently convex, 
lateral angles rounded. Ventral face moderately convex. Aperture about trans- 
verse, as indicated by the concentric strize and lines of growth. Shell of medium 
thickness. 
Surface of the shell transversely or concentrically striated by somewhat irreg- 
ular, raised, sharp, fine, closely arranged striz; on the rounded central side a few 
slightly oblique, longitudinal, elevated lines occur near the larger end. 
The largest specimen has a length of 9 mm., with a width of 1 mm. at the 
smaller end and 1.75 mm. at the larger end. 
There is some variation in the transverse section of the shell, owing to difference 
in the convexity and flattening of the dorsal face. In some specimens, toward the 
apical end, the section is a rather narrow ellipse. 
The elliptical section and the fine, raised, transverse strie serve to distinguish 
this species from any other known to me. 
Formation and Locality—Middle Cambrian: (C57) Limestone nodules in the 
lower shale member of the Kiu-lung group [Blackwelder, 1907a, pp. 37 and 4o 
(first list of fossils)], 3 miles (4.8 km.) south of Kao-kia-p’u, and 4 miles (6.4 km.) 
north of Sin-t’ai-hién, Sin-t’ai district, Shan-tung, and (C4) limestone nodules at 
the base of the lower shale member of the Kiu-lung group [Blackwelder, 1907a, pp. 
37 and 40 (second list of fossils), and fig. 10 (bed 4), p. 38 J, 3 miles (4.8 km.) south- 
west of Yen-chuang, Sin-t’ai district, Shan-tung, China. 
Collected by Eliot Blackwelder. 
This species is very abundant in the Dorypyge richthofeni zone of Manchuria: 
Middle Cambrian, (35n and 35r) Fu-chéu series; limestones near the base of the 
