78 RESEARCH IN CHINA. 
ican Pacific Province species of Acrotreta it most nearly approaches A. idahoensts 
Walcott [1912b, plate Lxv, figs. 1, 1a-7; plate Lxvimt, figs. 2, 2a-g] in the external 
form of the valves. The vascular markings on the interior of the dorsal valve 
differ in detail, as may be seen by comparing them. 
Formation and Locality—Middle Cambrian: (35q) Fu-chdéu series; about 200 
feet (61 m.) above the white quartzite [see Blackwelder, 1907), p. 92, for general 
stratigraphic relations], collected in a low bluff on the shore of Tschang-hsing-tau 
Island, east of Niang-niang-kung, Liau-tung, Manchuria, China. 
Collected by J. P. Iddings and Li San. 
Acrotreta sp. undt. 
In the Upper Cambrian limestone a single dorsal valve has been found at each 
of two localities (C56 and C68) that resembles the dorsal valve of A. pacifica, 
[p. 75] but in the absence of ventral valves I shall not attempt to identify them with 
any described species from the Middle Cambrian, or describe as new species. 
Formation and Locality——Middle Cambrian: (C56) Lower part of Ch’au- 
mi-tién limestone, 25 feet below the top of Pagoda Hill |Blackwelder, 19074, p. 42 
(part of last list of fossils)], 1 mile (1.6 km.) west of Tsi-nan, Shan-tung, and (C68) 
upper part of the Ch’au-mi-tién limestone [idem, p. 36 (part of third list of fossils)], 
on crest of ridge east of Ch’au-mi-tién, 200 yards (183 m.) north of the wayside 
shrine, Ch’ang-hia district, Shan-tung, China. 
Collected by Eliot Blackwelder and Li San. 
Genus DISCINOPSIS Matthew. 
Discinopsis (Matthew MS.) Haty and CLarKE, 1892, 11th Ann. Rept. State Geologist New York for 
1891, pp. 250-251. (Described.) 
Discinopsis Matthew, Hatt and CLARKE, 1892, 45th Ann. Rept. New York State Museum for 1891, 
pp. 566-567. (Copy of preceding reference.) 
Discinopsis Matthew, Hay and CLARKE, 1892, Nat. Hist. New York, Paleontology, vol. vin, pt. 1, 
pp. 105-106. (Described and discussed as a new genus.) 
Discinopsis Matthew, Wa.LcoTT, 1908, Smithsonian Misc. Coll., vol. nin, No. 4, plate x1, and pp. 142 
and 146. (Classification of genus.) 
Discinopsis Matthew, Wa.LcotTT, 1912, Monogr. U. S. Geol. Survey, vol. LI, p. 720. (The original 
description of Acrotreta ? gulielmi is copied and the genus is discussed under Discinopsis gulielmt, 
pp. 720-721). 
Discinopsis gulielmi (Matthew). 
The original diagnosis of the genus by Matthew was combined with that of 
the type species, Acrotreta ? gulielmi, as follows: 
“Shell subcircular in outline. Surface depressed-conical, apices eccentric, not 
marginal. Pedicle valve with the apex truncated by acircularforaminal aperture (?). 
The interior of this valve is characterized by a pair of deep, diverging furrows, 
passing forward from the beak or internal foraminal opening, in broad curves 
which converge toward the anterior margin but without meeting. These furrows 
enclose a thickened and somewhat elevated central area, which in the subumbonal 
region is apparently free, projecting for a short distance, like a narrow, triangular 
shelf, beneath which the foramen probably opened. ‘The interior opening of the 
foramen is, however, not apparent on any of the specimens examined, for, as usually 
preserved, the matrix has adhered to this subapical cavity, and in a single example 
only is the shelf-like character of the median area distinctly demonstrated. A faint 
longitudinal ridge passes from the apex of the shelf to the anterior margin, but no 
other markings are discernible on the interior except faint radiating or slightly 
undulating, probably vascular lines. 
