DESCRIPTION OF GENERA AND SPECIES. gl 
the end of 4 by 5 mm. The largest diameter at the aperture was probably about 
Io mm. 
The generic reference of this specimen is doubtful, but in the absence of the 
outer shell it is not possible to determine the generic relations. 
Formation and Locality.—Upper Cambrian: (C46) Light gray, crystalline lime- 
stone on the Ch’ang-hia limestone [Blackwelder, 19074, p. 33 (fourth list of fossils)], 
at Ch’au-mi-tién, Shan-tung, China. 
Collected by Eliot Blackwelder. 
Helcionella rugosa chinensis (Walcott). 
Plate 5, Figure 8. 
Stenotheca rugosa chinensis WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxrx, p. 16. (Described and 
discussed as a new species essentially as below.) 
In its general form this shell is closely related to Helctonella rugosa; it is, 
however, more elevated and more broadly oval in outline than the typical forms 
of H. rugosa. ‘The surface is marked by a number of moderate undulations, or low, 
concentric ridges, and numerous very fine, concentric strize of growth; with a strong 
lens fine radiating striz are visible. 
The type and only specimen in the collection has a longer diameter at the aper- 
ture of about 1o mm., with a height of 7 mm. to where the apex is decorticated; at 
this point the oval section has a length of 2.5 mm., with a width of 1.5mm. The 
apex is broken off at a smooth, slightly convex septum. 
This specimen is of unusual interest, owing to the presence of a septum toward 
the apex. Informit resembles most closely H. rugosa acutacosta (Walcott) [18914, p. 
617, plate 74, figs. 2, 2a—b], but differs from that variety in the presence of rounded 
instead of acute costae. From H. rugosa it differs in being elevated and more or 
less conical. 
Formation and Locality—Lower Cambrian: (C3) Lower part of the Man-t’o 
shale formation [Blackwelder, 1907a, p. 28 (list of fossils at bottom of page), and 
fig. 8a (bed 20), p. 28], on the southeast slope of Hu-lu-shan, 2.5 miles (4 km.) 
southwest of Yen-chuang, Sin-t’ai district, Shan-tung, China. 
Collected by Eliot Blackwelder. 
Helcionella rugosa orientalis (Walcott). 
Plate 5, Figures 15, 15a. 
Stenotheca rugosa orientalis WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxrx, p. 16. (Described and 
discussed as a new species essentially as below.) 
This variety is founded upon a small, slender shell with a rounded, oval aper- 
ture. In form it is between Helcionella rugosa acutacosta (Walcott) [1891a, p. 617, 
plate 74, figs. 2, 2a-b] and H. rugosa erecta Walcott [idem, fig. 4], being slender, 
slightly arched, and cornucopia-like. Surface marked by strong, sharply angular, 
concentric ridges, with broader U-shaped furrows between them, and numerous fine 
concentric strie. The average length of the shells of this species is 3 mm., with a 
diameter at the aperture of 1.5 to 1.75 mm. 
Formation and Locality—Middle Cambrian: (C21) Ocher-mottled phase of 
purple-gray limestone in the middle of the oolitic Ch’ang-hia formation [Blackwelder, 
1907, p. 33 (second list of fossils)], at Ch’ang-hia, and (C18) dark gray oolitic 
limestone about 400 feet (120 m.) above the base of the Ch’ang-hia limestone [idem 
(third list of fossils)], in cliffs 1 mile (1.6 km.) east of Ch’ang-hia, Shan-tung, China. 
Collected by Eliot Blackwelder. 
