92 RESEARCH IN CHINA. 



Helcionella ? ? simplex (Walcott). 

 Plate 5, Figure u. 



Stenotheca simplex WAI.COTT, 1906, Proc. U. S. Xat. Mus., vol. xxx, p. 573. (Described and discussed 

 as a new species essentially as below.) 



Shell small, depressed conical, with the apex situated about one-sixth the dis- 

 tance from the front to the posterior margin ; the point of the apex is broken away ; 

 aperture subcircular, a little broader than long. 



Surface with fine concentric stria? and lines of growth and a few fine radiating 

 lines. There is a trace of a shallow furrow extending from the apex toward the 

 central portion of the anterior margin. 



The greatest diameter of the type and only specimen is 2 mm. 



This species differs widely from other known species from China. It may be 

 compared with some varieties of the young of Helcionella nigosa, but it differs in 

 the aperture being broader and in not having a rugose surface. The continuous 

 concentric striae and absence of an area indicate that it is probably a gastropod, but 

 its generic reference is doubtful. The flattened space or shallow median furrow 

 suggests a brachiopod allied to Acrotreta, but the calcareous shell is not in accord 

 with that interpretation. 



Formation and Locality. Middle Cambrian: (70) Oolitic limestone about 

 30 feet (9 m.) above the base of the Ki-chou limestone [Willis and Blackwelder, 1907, 

 p. 144 (last list of fossils)], 4 miles (6.4 km.) south-southwest of Tung-yii, Shan-si, 

 China. 



Collected by Eliot Blackwelder. 



PTEROPODA. 



Genus HYOLITHES Eichwald. 

 Hyolithes cybele Walcott. 



Plate 5, Figures 16, i6a-c; Plate 6, Figure 7. 



Hyolithes cybele WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 17. (Described and discussed as 

 a new species essentially as below.) 



Form an elongate, subtriangular pyramid, gradually and regularly tapering to 

 an acute extremity. The apical angle of the dorsal side is about 15. Transverse 

 section rounded subtriangular; the ventral angle is rounded and the lateral angles 

 are slightly rounded off. Dorsal face moderately convex and curving very slightly 

 from the apex to the anterior spatulate portion. Ventral face strongly and regu- 

 larly convex transversely. Aperture oblique, the margin extending on the dorsal 

 side; the peristome on the ventral side is slightly curved forward. 



Surface marked by concentric, transverse, more or less obscure lines and striae 

 of growth; the cast of the interior shows on the ventral face three or four obscure 

 longitudinal lines, the central one of which is the strongest. 



The largest specimen in the collection has a length of 24 mm., with a width of 

 7 mm. at the aperture. 



The body of the associated operculum is semicircular, moderately convex on 

 the outer side externally, and concave within. The ventral wing as seen on the 

 outside is semicircular-convex, rising toward a point at the center of the transverse 

 side. The dorsal limb is nearly flat, rising, as far as can be determined from a broken 

 specimen, at an angle of about 100 from the plane of the body of the operculum. 



