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 i mm. 



This species resembles, in its slender tube and nearly circular section, Hyolithes 

 communis Billings [Walcott, 18910, plate 77, figs. 3, 30-^]. It may be com- 

 pared with Ortlwtlicca stylus Holm [1893, p. 52, plate i, 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 Orthothcca tcre- 

 tinsculus Linnarsson as illustrated by Holm in his memoir on Hyolithiclge [1893, p. 

 51, plate i, figs. 21-24]. 



Formation and Locality. Middle Cambrian: (023) Upper part of thin bedded, 

 gray oolitic limestone at the base of the Ch'ang-hia formation [Blackwelder, 19070, 

 p. 32 (second list of fossils), and fig. 6 (bed 20), p. 25], 50 feet (15 m.) below the base 

 of the cliffs i mile (1.6 km.) east-southeast of Ch'ang-hia, Shan-tung, China. 



Collected by Eliot Blackwelder. 



Orthotheca delphus Walcott. 

 Plate 6, Figures i, la-b, 5, 6. 



Orthotheca delphus WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, 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 striae 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 striae; 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 i 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 striae serve to distinguish 

 this species from any other known to me. 



Formation and Locality. Middle Cambrian: (057) Limestone nodules in the 

 lower shale member of the Kiu-lung group [Blackwelder, 19070, pp. 37 and 40 

 (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-hien, Sin-t'ai district, Shan-tung, and (0-1) limestone nodules at 

 the base of the lower shale member of the Kiu-lung group [Blackwelder, 19070, pp. 

 37 and 40 (second list of fossils), and fig. 10 (bed 4), p. 38 ], 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 richthojeni zone of Manchuria: 

 Middle Cambrian, (35 n and 35 r) Fu-chou series; limestones near the base of the 



