84 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



I propose to make it a sub-genus of Protothaca with the name of 

 Ehonudea, from jw/naXeo^, strong. It can be defined thus : — 



Sub-</enns. 



Rhomalea, J. -Br., 1914. Tj-pe, Venus rufa, Lamarck. Habitat, 

 Peru. 



Shell similar to Protothaca, but nearly smooth ; showing faint 

 radial strife all over the surface, obscured on the anterior side by 

 stronger concentric strioe. Ligament very large and prominent. 

 Hinge-plate curved and both posterior teeth very short. Interior 

 margins smooth, pallial sinus sharply pointed. Pedal scar small and 

 separate from that of adductor. Venus kennprhji may perhaps be 

 associated with rufa, as its dentition and sinus are similar. 



Genus Samarangia, Ball, 1902. 



Shell oval or sub-quadrate, concentrically striated or minutely 

 reticulated. Inner margins of valves smooth. Lunule flat, circuni- 

 scribed. Escutcheon not defined. Hinge-plate short, with a flat or 

 concave anterior expansion. Teeth divergent, three in eatdi valve, 

 the left anterior and median united at top, and fitting over the right 

 anterior; left posterior generally long and partly confluent with the 

 nymph. Pallial sinus fairly deep. Pedal scar more or less confluent 

 with that of the adductor. 



Samarangia, s.a. Type, Venus qnadrangularis, Ad. & Rve. 



Shell solid, sub-quadrate, dull white. Ligament long. Valve- 

 margins smooth. Pallial sinus horizontal, linguiform, and pointed. 

 Pedal scar oval, very narrowl}" confluent with that of adductor. 

 So far as my own knowledge goes, this section only includes 

 quadrangiilaris, lenticularis, Sow., and exalbida, Cliem. 



Suh-genera. 



Mercimonia, Dall, 1902. Type, T^-mms ^<T?^rty/, Cossmann (Eocene 

 fossil). 



Shell sub-orbicnlar, substantial, convex, concentrically striated. 

 Lunule feebly defined, ligament sunk. Hinge-plate deep, and 

 anterior concavity well developed. Right posterior tooth widely 

 bifid, and both posteriors curved. Left median and anterior united 

 at top and both entire. Posterior marginal gi-oove long. Pedal scar 

 confluent with that of adductor. Pallial sinus variable in depth and 

 shape. 



A perusal of the description given by Messrs. Cossmann and 

 Peyrot of V. dujardini of thp Bordeaux Miocene, and the examination 

 of a left valve, for which I am indebted to Professor Peyrot, have 

 convinced me that it belongs to the same group as the Eocene shells 

 described by M. Cossmann and mentioned by me in a previous 

 volume of these Proceedings (vol. viii, p. 169). 



Textivenus, Cossmann, 1886. Type, Venus texta. Lam. (Eocene). 



Shell small, oval, ornamented with raised obliquely reticulate 

 strife. Valve-margins smooth. Only right posterior margin grooved. 

 Pallial sinus ascending. Pedal scar narrow, and confluent with that 

 of adductor. 



