OUDKU II 



ANOMALODESMACEA 



889 



podial foramen. Shell thin, equivalve, gaping, edentulous, or with an obscure sub- 



umbonal tubercle; li<i<mn'nt, and resilium external, opisthodetic, seated on nyiui>! . 



area obsolete or obscure, not amphidetic ; beaks entire; pallial sinus well <///./. 

 marine. Trias to Recent. 



Pholadomya, Sow. (Figs. 690-692). Shell thin, .-iib-ovate, with radial an<l con- 

 crnlric sculpture, inflated, and with ratlin- pruniinenl beak> : hinge edentulous, or 

 with ah obscure thickening; scars feel.le, pallial >iniis moderately deep. In the 



Fio. 693. 



Gonimnya Duboisi, Ag. Inferior Oolite ; Bayeux, 

 Calvados. A, Shell, ift. B, Surface showing 

 punctations, magnified. 



Fio. c.'.' t. 



Homomya (Arcomya) calceiformis, Ag. Inferior 

 Oolite ; Les Moutieux, near Bayeux, CuvadOS. - ,. 



posterior dorsal region the radial sculpture is usually feeble or absent. Lower Lias to 

 Recent ; formerly very abundant, but now represented by but a single species from 

 the Antilles. 



Procardia, Meek. Includes those forms with an escutcheon. Jura. 



Goniomya, Ag. (Fig. 693). With V-shaped sculpture. Lias to Cretaceous ; very 

 plentiful in Middle and Upper Jura. 



Homomya, Ag. (Arcomya, Myopsis, Ag. p.p.), (Fig. 694). Distinguished from tin- 

 typical Pholadomyas by its smooth or very finely sculptured shell, without rib.-. 

 Trias to Cretaceous. 



(?) Machomya, Plectomya, Loriol ; Mactromya^ Ag. Jura and Cretaceous. 



Family 4. Anatinidae. DalL 



Soft parts like Pholadomya, the foot small and grooved, ventral foramina small, and 

 the siphons with a horny integument, not entirely retractile. Shell sub-equivalve, tr\nn-<it<\ 

 or gaping behind, edentulous, the resilium internal between 

 two spoon-like chondrophores vertically directed and often 

 supported by buttresses ; ligament obsolete or absent ; area 

 obsolete; beaks transversely fissured; pallial sinus well 

 marked ; monoecious ; marine. Jura to Recent. 



Anatina, Lam. (Platymya, Cerconnja, Ag.; Plicomya, Flo 6y5 



StoL), (Fig. 695). Shell thin, nearly equivalve, con- Anat : na pnilwt<tt ' Zittel . Upper 

 centrically but feebly sculptured, posterior side shorter Cretaceous ; Gosau Valley, Austria, 

 than the anterior. Jura to Recent. 



Periplomya, Anatimya, Conrad ; Ehynchomya, Agassiz. Cretaceous. 



Family 5. Periplomidae. Dall. 



Shell sub-nacreous, conspicuously inequivalve, nearly closed, edentulous; the 

 internal, between two anteriorly or vertically^directed chondrophores, often buttressed, the 

 lithodesma rarely wanting; ligament and area absent; beaks fissured ; pallial sinus 



