64 rUOCEEDINGS OF THE MALACOUJGICA L SOCIETY. 



or corrugated. Lunule generally small ami impressed. Escutcheon 

 seldom well defined ; ligament generally deeply sunk. Hinge-plate 

 deep aTid strong ; cardinal teeth ;3-."5, with one anterior lateral in the 

 left and two small ones in the right valve ; right posterior cardinal 

 bitid, and often a supplementary tooth-like ridu;e at the base of the 

 right nymph. Left posterior cardinal long and extending obliquely 

 across the hinge-plate. Right i)ost(M-ior margin generally grooved for 

 a short distance, but the left anterior only in Sinodia and Cordiopsis . 

 Pedal scar confluent with that of the adductor. 



Dosifiia, s.s. 'i\vpe, D. africana, Gray. 



Escutcheon depressed. Anterior lateral large and strong. Left 

 middle cardinal broadly bifid. Pallial sinus long, narrow, ascending. 



Hection Bosinella, Dall. 1902. Type, D. anyulom, Phil. 



Lunule shallow. Escutcheon ill-defined. Anterior lateral small 

 or obsolete ; left middle cardinal broad and bifid. Pallial sinus very 

 deep, ascending and rounded at the end. 



Section Austrodosinia, Dall. 'Pype, D. ajins, Phil. 



Kscutcheou ill-defined. Anterior lateral strong and rugose. Left 

 nii<ldle cardiiuil entire and solid. Pallial sinus short, horizontal. 



Section Phacosotna, J. -Br., 1912. Type, D.japonica, lleeve. 



Escutcheon well-defined bv lamellose ridges, and the inner edges 

 turned up on each side of the ligament. Anterior lateral strong and 

 left median caniinal oblique, rugosely striated, but not bifid. Pallial 

 sinus deep and angular. 



Section Pedujiculus, Da Costa ( = Orhindus, Megerle). Type, 

 D. exoleta, Linn. 



Escutcheon not defined. Anterior lateral small, and left middle 

 cardinal obscurelj^ and unequally bifid. Pallial sinus deep, ascending, 

 rounded or obtusely angular. 



Section Dosmidia, Dall, 1902. Type, D. concentrica, Born. 



Escutcheon not defined and lunule very little impressed. Anterior 

 lateral small and pustular. Left middle cardinal broad and obscurely 

 bifid. Pallial sinus deep, angular, and ascending. Dorsal margins 

 not grooved. 



Sub-ffenera. 



Sinodia, J. -Br. Type, Dosinia trigona, Pteeve. 



Shell convex. Lunule superficial, not impressed. Escutcheon not 

 defined. Anterior lateral strong and distant. Middle left cardinal 

 solid and central. Both left anterior and right posterior margins 

 grooved for some distance. Pallial sinus rather short and rounded. 



Since the publication of my paper on Dosinia I have discovered 

 that Cytherea gonldi, lleeve, belongs to this sub-genus. The type is 

 in the British IMuseum, and Mr. E. A. Smith writes that "it is 

 certainly a Sinodia, the hinge being exactly the same as in trigona'". 



Cordiopsis, Cossmann. Type, Cytherea incrassata, Sow. 



Shell thick, sub-orhicular, convex and cordiform, with prominent 

 incurved umbones. No lunule or escutcheon. Left anterior lateral 

 small and becoming obsolete with age ; middle cardinal thick, rugose, 

 and central. Left anterior and right posterior dorsal margins grooved. 

 Pallial sinus short, sub-angular, ascending. 



