NO. 4 CAMBRIAN FAUNAS OF CHINA 75 



Interiors of the ventral valve indicate that the area was relatively 

 shorter than that of L. similis (Walcott). Most of the shells in the 

 limestone are less than 2 mm. in length ; a few ventraf valves in the 

 shale are 3 to 5 mm. long. 



Formation and locality. — Middle Cambrian: (35q and 36h) Fu- 

 chon series; abont 200 feet (61 m.) above the white quartzite ; also 

 in shales about 130 feet (40 m.) above the white quartzite; collected 

 in a low bluff on the shore of Tschang-hsing-tau island, east of 

 Niang-niang-kung, Liau-tung, Manchuria, China. 



Collected bv ]. P. Iddings and Li San. 



A form flattened in the shale of locality 36f, which is much higher, 

 but in the same section as the locality represented by L. marcia, has 

 the outline of the latter species and is tentatively referred to it. This 

 gives an extended stratigraphic range for the species, but not so 

 great as that of L. similis (Walcott) which occurs in both the Mid- 

 dle and Upper Cambrian. 



ACROTRETA VENIA, new species 

 Plate 14, figs. 4, 4a 



Acrotreta venia is closely related to A. shantKugeiisis Walcott. 

 It differs in having a slightly less elevated ventral valve and a more 

 distinct and broader flattening of the posterior side and margin. The 

 faintly defined false area and apex of the valve curve slightly over the 

 porterior margin. The dorsal valve does not show the median 

 depression of the dorsal valve of A. shantiingensis. Of the Amer- 

 ican Pacific Province species of Acrotreta, it most nearly approaches 

 A. idahocnsis (Walcott) 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. 



Foniiation and locality. — Middle Cambrian: (35q) Fu-chuu series; 

 about 200 feet (61 m.) above the white quartzite, 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. 



ORTHOTHECA GLABRA, new species 



Plate 14, figs. 5, sa 

 Form an elongate, slender, rounded tube, with the dorsal face less 

 convex than the sides and ventral face. Transverse section round, 



