CONCHIFERA. 323 



Shell thin, ventricose, concentrically furrowed in front ; escutcheon long and 

 flat. Silurian Carb. Europe. 



CEROMYA, Agassiz. 



Etym. Keraos horned, mya, mussel. 



Type, C. concentrica (Isocardia) Sowerby, Min. Con. 491, fig. 1. 



Shell Isocardia-shaped, slightly inequivalve ? very thin, granulated, often 

 eccentrically furrowed; ligament external; hinge edentulous; right valve 

 with an internal lamina behind the umbo ; pallial line scarcely sinuated ? 



Fossil, 14 sp. Inf. Oolite . Green-sand ? Europe. 



Sub-genus ? Gresslya (sulcosa) Ag. (Amphidesma and Unio. sp. Phil.) 

 Shell oval, rather compressed ; urnbones anterior, incurved, not prominent ; 

 valves thin, close, smooth or concentrically furrowed ; pallial sinus deep. 

 Fossil, 17 sp. Lias Portlandian. Europe. The lamina within the pos- 

 terior hinge-margin of the right valve produces a furrow in the casts, which 

 are more common than specimens retaining the shell. 



? CARDIOMORPHA, Koninck. 



Type, C. oblonga (Isocardia) Sby. (not Kon.) Carb. lime. 



Shell Isocardia-shaped, smooth or concentrically furrowed, umbones pro- 

 minent, hinge edentulous ; hinge -margin with a narrow ligamental furrow, 

 and an obscure internal cartilage-groove. 



Fossil, 38 sp. L. Silurian Carb. N. America, Europe. 



EDMONDTA, Koniuck. 



Ex. E. sulcata, Ph. (T. Pal. Soc. 1850, PL XX. fig. 5.) Carb. Brit. 



Syn. Allorisma, King (part). Sanguinolites, M'Coy (part). 



Shell oblong, equivalve, thin, concentrically striated, close ; umbones an- 

 terior; ligamental grooves narrow, external; hinge-line thin, edentulous, 

 furnished with large oblique cartilage-plates, placed beneath the umbones, 

 and leaving space for an ossicle ? pallial line simple ? 



Fossil, 4 sp. Carb. Permian. Europe. 



LYONSIA, Turton, 1822 (not R. Brown). 



Syn. Magdala, Leach, 1827. Myatella, Brown. Pandorina, Seaochi. 



Type, L. Norvegica, PI. XXIII. fig. 10. 



Shell nearly equivalve, left valve largest, thin, sub-nacreous, close, trun- 

 cated posteriorly; cartilage plates oblique, covered by an oblong ossicle; 

 pallial sinus obscure, angular. Structure intermediate between Pandora and 

 Anatlna ; outer layer composed of definite polygonal cells. 



Animal with the mantle closed ; foot tongue-shaped, grooved, byssiferous ; 

 siphons very short, united nearly throughout, fringed; lips large, palpi 

 narrow, triangular. 



Distr. 9 sp. Greenland, N. Sea, Norway, W. Indies, Madeira, India, 

 Borneo, Philippines, Peru. 



