DESCRIPTION OF GENERA AND SPECIES. 75 
The data for comparison of this species with described species from America 
and Europe are too limited to be of value. A comparison with Acrothele (Red- 
lichella) granulata (Redlich)' Walcott [1912, p. 633, plate Lv1, figs. 2, 2a—m], of the 
Salt Range, India, shows a strong similarity in the interiors of the dorsal valves; 
but I do not think it is probable that the two forms are specifically identical, as 
the interiors of the valves of several species of Acrothele appear very much alike. 
Formation and Locality——Middle Cambrian: (C57) In 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, China. 
Genus ACROTRETA Kutorga. 
For description and discussion of the genus Acrotreta see Monogr. U. S. 
Geol. Survey, vol. LI, 1912, pp. 671-674. 
Acrotreta lisani Walcott. 
Plate 3, Figures 9, 9a—c. 
Acrotreta liant WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxv, p. 300. (Described and discussed 
as below as a new species. Li San’s name was at that time believed to be correctly written as 
Lian, hence the form of the specific name.) 
Acrotreta lisani WALCOTT, 1912, Monogr. U.S. Geol. Survey, vol. 11, pp. 692-693, plate Lxvu, figs. 
3, 3a-c. (A copy of the preceding reference.) 
Shell small, about 1.5 mm. in diameter; outline of aperture subcircular, the pos- 
terior side being slightly transverse. Ventral valve conical, with the apex a little in 
advance of the posterior margin; false area indefinite, except for a rather strong, flat 
furrow that extends from the apex to the margin; the elevation of the valve is about 
two-thirds of the diameter atits aperture. Dorsal valve slightly convex, apex mar- 
ginal. Surface of shell marked by fine, concentric striz and lines of growth that on 
the dorsal valve tend to form low ridges toward the outer margins. 
This species is the representative of the American Acrotreta idahoensis sulcata 
Walcott [19120, p. 690, plate LXV, fig: 5]. It has the same type of false area, and the 
ventral valve is of average height. The specific name is given in recognition of 
Li San, Mr. Willis’s faithful Chinese interpreter. 
Formation and Locality—Middle Cambrian: (C22) Ch’ang-hia limestone in 
upper oolitic portion [Blackwelder, 1907a, pp. 22 and 33 (part of last list of fossils)], 
at Ch’ang-hia, Shan-tung, China. 
Collected by Eliot Blackwelder. 
Acrotreta pacifica Walcott. 
Plate 4, Figures 1, 1a-f. 
Acrotreta pacifica WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxvii, p. 301. (Described as below as 
a new species.) 
Acrotreta pacifica WaLcorTT, 1912, Monogr. U.S. Geol. Survey, vol. LI, p. 699, plate LxIx, figs. 6, 6a-e. 
(A copy of the preceding reference.) 
Ventral valve a high cone, with the apex a little in advance of the posterior 
margin; base circular, with the exception of a slight flattening on the posterior side; 
apex acute and pointing upward; false area only a slight flattening of the shell from 
the apex to the margin. The largest ventral valve has a diameter and height of 
about 1.5 mm. Surface marked by fine, concentric strie that continue without 
noticeable deflection across the false area. 


1 Mobergia granulata Redlich, 1901, Mem. Geol. Surv. India, n. ser., vol. 1, p. 5, plate I, figs. 11-18. 
