538 TRANSACTIONS OF THE WAGNER FREE 



B. Diogenodonta. 

 Laterals normally one or two, and cardinals three or less, in any one 

 group. 



Superfamily CYPRICARDIACEA. 



Lobes of the mantle partially closed ventrally ; anterior lateral laminae ab- 

 sent, or grouped with the cardinal teeth, short and obscure. 



Family PLEUROPHORID^? 



Gills with the outer limb appendiculate, smaller than the inner, united 

 behind the foot to each other and to the siphonal septum; palpi moderate ; 

 foot compressed, grooved, sometimes byssiferous; mantle with a moderate 

 pedal and two siphonal openings, the siphonal orifices usually not produced 

 into tubes ; dioecious, marine. 



Shell substance cellulo-crystalline ; valves equal, free, closed ; adductor 

 scars subequal, free from the pedal scars ; pallial line entire, or feebly sinu- 

 ated ; area obscure ; ligament external or seated in a groove, parivincular ; 

 margins of the valves usually plain ; hinge with one left and two right poste- 

 rior laminse, the anterior laminae absent or confused with the cardinals ; two or 

 three cardinal teeth in each valve, of which the posterior in both valves is sub- 

 parallel to the dorsal shell-margin, and in the right valve is usually bifid. 



Devonian to recent fauna. 



E.x. Subfamily Pleurophorincz ; Pteurophorus, Cypricardella, Paleocardila, Mecynodon, 

 Anisocardia, Astartella, {Cypricardia=) Trapezium, Coralliophaga. 

 Subfamily Veniellince ; Veniella, Venilicardia, (Cyprina=) Arclica. 



Superfamily ASTARTACEA 



Lobes of the mantle free ventrally ; lateral laminae obscure, when present 

 distant from the cardinals. 



Family CURTONOTID^? 



Shell short and heavy, with subterminal beaks ; valves free, equal, closed ; 

 area obscure ; ligament as in AstartidcB ; adductor scars, especially the ante- 

 rior, deep ; pallial line simple ; hinge-plate broad, without lateral laminje, the 

 formula of the cardinals ^-^-gxo °'' Kioi! marine. 



Devonian and Carboniferous. 

 Ex. Curtonotus, Prosoccelus, Protoschizodus, Kejersteinia. 



This group is inserted in conformity with the opinion of Neumayr, who 

 regards it as the radical of the Astartidte. 



Family ASTARTIDyE. 



Gills not united behind the foot, the outer limb smaller, without appendix ; 

 palpi moderate ; foot compressed, grooved, not byssiferous ; lobes of the man- 



