(iv) 24 Palasontologia Sinica Ser, B- 



Pedicle valve convex, ribs become more pronounced in tlie frontal part of the 

 shell. Ribs increase by bifurcation and with nodes on their crests; they are broad, the 

 interspaces being narrower than the ribs. A median sinus moderately distinct extends 

 from the umbo to the frontal margin of the shell. 



The plications of the shell and the form suggest Huenella ; but the nodes on the 

 crests of the ribs serve to distinguish it. All species of Huenella except etheridgii are 

 from the Upper Cambrian. 



Nothing is known of the interior of the shell. 



This species is characterized by its transverse form. Inroad radiating ribs with 

 nodes on their ci'ests and the less pronounced median sinus. 



Measurements : — 



Length. 6 mm. 



Width 9 mm. 



Horizon and Locality: — Middle Cambrian: from Changhia limestone of Cheng- 

 shan, 2 H from Luan-Hsien, Chihli (Coll. K. S. Hsu ^^^) . 



This species is named after the Japanese Palaeontologist Dr. I. Hayasaka. It is 

 represented by several crushed valves. It is associated with Damesella blackivelderi var 

 mi)ior, Dorypyge richthojeni etc. 



Genus EOORTHIS Walcott 

 Eoorthis shakuotunensis Sun (sp. nov.) 



Plate I, Figs. 13a-13b. 



This species is represented by a number of the pedicle valves and one interior of 

 the pedicle valve. 



Shell moderately convex, subquadrate in outline with angular cardinal extremi- 

 ties. Hinge line usually forming the greatest width of the shell. Posterior margin on 

 both sides of beak straight, forming an angle of 160 degrees. Median fold faint on the 

 ventral valve. 



Surface marked by a few rounded radiating ribs, which where farthest apart 

 measure 3 in 2 mm; there are 1 or 5 fine striie between each pair of larger ones. The 

 ribs increase in number by interpolation and may appear at any distance from the beak, 

 usually becoming coarser near the frontal margin. 



