134 Mr. A. J. Jukes-Browne on 



few specimens liave come into the possession of conclio- 

 logi^ts. 



Having recently received a shell from Mr. Y. Hirase, of 

 Kyoto (Japan), which 1 felt sure must be V. stimpxoni, as it 

 was clearly a Mercennria, and that is the only Japanese 

 species oE the group, I wrote to Mr. E. A. Smith about it. 

 He sent me a copy of Gould's description, but informed me 

 that the Museum did not possess a specimen, and advised 

 me to have the shell com{)ared with the type in the United 

 States Museum. Accordingly I sent it to Dr. P. Bartsch, 

 who has kindly compared it with the type and informs me 

 that it is undoubtedly the V. Himpsoni of Gould. 



Under these circumstances it seems desirable that the shell 

 should be figured and more fully described in English, for 

 Gould's description -was in Latin only, and ran as follows : — 



" Vemis (^}Jercenaria) stimpsoni. T. [/. e. Testa] solida, 

 cinerea, ovato-cordata, satis convexa, laminis erectis con- 

 centricis confertis disposite ornata ; umbonibus antemedianis 

 eminentibus, acutis, approximatis; facie dorsali antica con- 

 cava ; luinilS, profunda; extremitate antica compressa, 

 rotundata ; facie dorsali postica arcuata, declivi, impressa, 

 nihil nisi striata ; extremitate postic^ satis acuta : cardo 

 validus; cavositas et apophysis ligamentalis aurantiaci ; 

 sinu siphonali minime profundo ; margine interna simplici. 

 Long. 3'7 ; alt. 3-3 ; lat. 1'7 poll. Inhabits Hakodadi, 

 6 fathoms." 



Tlie Mercenaria group belongs to what should be regarded 

 as the restricted genus Veyius, though I have come to that 

 conclusion on different grounds from Dr. Dall, and differ from 

 liim in regarding the genus as a much more comprehensive 

 group, for I can see no geneiic distinction between it and 

 Chione. 



The characters possessed in common by Mercenaria and 

 Chione are : that the external sculpture of the shell is more 

 or less cancellate, the concentric lamellae predominating, but 

 the radiate riblets show themselves in the crenulated inner 

 margins of the valves ; that the lunule is impre.-sed and the 

 escutcheon is well defined ; that all have a thick hinge-plate, 

 bearing three cardinal teeth, but no laterals ; and, finally, that 

 the pallial sinus is small, triangular, and pointed. 



Mercenaria differs from the typical Chione in always 

 having a rugose area on the nymphal plate of the right valve 

 and on the back of the posterior tooth of the left ; such areas 

 being only present in a few species of Chione. The posterior 

 and middle teeth of the right valve are deeply grooved or 



