Hor. Wandrawandian Series: (Jerringong Series. 



Obs. This is one of tlie most common species at Barrier, 

 and like most of the other pelecypods, specimens are well 

 preserved. 

 Mytilus sp. (Type A.) 



Description. — Shell small and wedge-shaped ; contour of 

 united valves regularly cordate. Nearly equivalve, the 

 left valve being slightly the larger. Ventral and posterior 

 margins rounded. Anterior margin straight. Umbos ter- 

 minal, fairly prominent, and twisted anteriorly, overhanging 

 the anterior margin. Hinge line short, curved and eden- 

 tulous. Shell of moderate comparative thickness, and 



Loc. Barrier (l»: Grassy Gully (F). 



Hor. Wandrawandian Series. 



Obs. The best specimens were found at Barrier where 

 they are very abundant and well preserved; but internal 

 casts are also fairly abundant at Grassy Gully. This and 

 the following species (type B) will on further investigation 

 probably prove to be new, for no very small mytiloid shells 

 have as yet been described from the Permo-Oarboniferous 

 of New South Wales. Both species are however held, 

 pending the work of Messrs. Etheridge and Dun on the 

 genus, in which they will be finally dealt with. 



Mytilus sp. (Type B.) 



This is a slightly larger shell than the preceding, with 

 sharp pointed umbos, recurved anteriorly. The posterior 

 margin is broadly expanded, and rounded, the anterior 

 margin incurved and slightly concave, the umbos extending 

 beyond. Hinge line fairly long and straight. Ornamenta- 



