Manchester Memoirs, \\>l.LV., No.^. 



Plate. 



Flwtos by J ■ W. Jackson, F.G.S. 



Typical Keuper pktorum, 



Marple form, showing the forward throw of the umbo. 



Burnley Canal form. 



R. Foss form. 



L. Rudyard form. 



Typical non-Keuper form. 

 G. Young Anodons, showing umbonal markings [e. coll. K. Standen], 

 H. U. pictorum [Marple] showing tumidus like umbo. 

 I. Typical U. pictonim umbo. 

 J. ,, U. tumidus markings. 



y ' r; f V ' i showing umbonal markings approachinj; AitoJon in type. 



