Vol I. Sun— Cambrian Faunas of North China (iv) 19 



Measurements : — 



Length 4.0 mm. 



Width 3.8 mm. 



This species resembles Obolus willisi Walcott from the Upper Cambrian and Mid- 

 dle Cambrian of Alabama, in form, but differs in the absence of the punctate character of 

 the surface and also in the character of the umbo and in size. 



Horizon and Locality: — Cambrian: from limestone inter-bedded in Manto 

 shale of Hung-shan-T'ou, UlUM Lin-Yu Hsien: collected by University excursion in 1923 

 vinder the direction of the author. 



Obolus taianensis Sun (sp. nov.) 



Plate I, Fig. 6 a, 6 b. 



Shell small, ovate in form, pedicle valve obtusely rounded; valves moderately 

 convex, the convexity increasing gradually from the margins to the umbonal portion of 

 the shell. 



Surface marked by concentric lines: when the outer layer of the shell is exfolia- 

 ted, numerous radiating striae will appear on the surface. The shell is formed of lamel- 

 lose layers, which make a strong thick shell. 



Measurements : — 



Length 5.9 mm. 



Width 6.4 mm. 



The shell figured by Walcott on Plate II fig. 2, from Kaolishan and provisionally 

 referred to 0. matinalis Hall may belong to this species, agreeing with it in general 

 form and size, though the length of Walcott 's specimen is slightly greater than the 

 Avidth. 



This species is distinguished by its oval shape, moderate convexity of the shell 

 and the lamellose character of the shell surface. It is represented by many individuals 

 which occur abundantly in that zone. 



Horizon anic Locality: — Upper Cambrian: associated with Ptychaspis subglobosa 

 Grabau in the upper beds of Kaolishan limestone (Coll. Y. C. Sun). 



Obolus luanhsiensis Grabau (mss.) (sp. nov.) 

 Plate I, Figs. 7 a-7 c. 



1883 LinguleUa sp. Kayser in Richthofen China, Vol- pi. Ill, fig- 2. 



