DESCRIPTION OF GENERA AND SPECIES. 63 
A ventral valve 3 mm. in width has a length of 2.75 mm. and a height of 1 mm. 
A dorsal valve with a width of 2.5 mm. has a length of 2 mm. and a height of 0.5 
mm. at the beak. 
In form the ventral valve of this species is not unlike that of Micromitra sculp- 
tilis (Meek) [p. 61], except that it is not so elevated and its surface is quite different. 
It is associated with M. sculptilis and the two varieties of Micromitra (Iphidella) 
pannula, ophirensis and maladensis. 
Formation and Locality.—Middle Cambrian: Fu-chdéu series: (35n and 35r) 
limestones and (36d) shales near the base, just above the white quartzite [see Black- 
welder, 1907), p. 92, for general section giving stratigraphic relations]; collected ina 
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. 
IPHIDELLA Walcott, Subgenus of MICROMITRA. 
For discussion of the subgenus see Monogr. U. S. Geol. Survey, vol. 11, 
I9I2, p. 359. 
Micromitra (Iphidella) pannula maladensis (Walcott). 
Plate 1, Figures 9, 9a. 
Iphidella pannula maladensis WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxviu, p.306. (Description 
of variety.) 
Micromitra (Iphidella) pannula maladensis (WaLcort), 1912, Monogr. U.S. Geol. Survey, vol. 11, p. 364, 
plate Iv, figs. 2, 2a-g. (Describes and illustrates the variety.) 
This beautiful shell has been found in Newfoundland with the Atlantic Province 
Middle Cambrian fauna and in southern Idaho with the Rocky Mountain Province 
fauna [Walcott, 1912, p. 364, Monogr. ui]. It differs from the variety ophirensis 
of this species, with which it is associated (35n) in having a more network-like 
surface of sharp elevated ridges, and from WM. (J.) pannula in having the surface 
network formed of sharper concentric ridges modified by fine, rounded, radiating 
ridges. These differences are shown by the illustrations on plate 1v, Monogr. 
U. S. Geol. Survey, vol. LI. 
Formation and Locality.—Middle Cambrian: (85n and 35r) Fu-chéu series; 
limestones near the base just above the white quartzite [see Blackwelder, 1907), 
p- 92, for general section giving stratigraphic relations]; collected in a low bluff on 
the shore of Tschang-hsing-tau Island, east of Niang-niang-kung, Liau-tung, Man- 
churia, China. 
Collected by J. P. Iddings and Li San. 
Micromitra (Iphidella) pannula ophirensis (Walcott). 
Plate 1, Figures 10, 10a—b. 
Iphidella pannula ophirensis WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxviu, p.306. (Characterized 
as a new variety.) 
Micromitra (Iphidella) pannula ophirensis (WaLcott), 1912, Monogr. U.S. Geol. Survey, vol. LI, p. 365, 
plate tv, figs. 4, 4a—f. (Describes and illustrates the variety.) 
This variety of Micromitra (Iphidella) pannula is represented by several fine 
specimens occurring in a limestone similar in character to the limestone at Ophir 
City, Utah, containing the American specimens [Walcott, 1912), p. 365]. In form 
and surface characters the shells from the two widely separated localities appear 
to be identical. 
Formation and Locality —Middle Cambrian: (35n) Fu-chdu series; limestones 
near the base, just above the white quartzite [see Blackwelder, 1907), p. 92, for 
general section giving 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. 
