292 EXPEDITION TO JAPAN. 



At the suggestion of Commodore Perry I have prepared with great care a list of all the shells 

 which have been described as being found at Japan and the adjacent islands. It is arranged 

 according to the system of Lamarck, and, as a reference, will be valuable to conchologists. 



The collection brought home was large and numerous, but, among them all, the following 

 only may be described as new. 



MY A JAPONICA. 



Plate 1, figs. 1 and 10. 



Testa ovata, convexa, incrassata, posterius rotundata — impressionibus muscularibus duabus, 

 lateralibus, distantibus, antica ovata, postica, quadrangularis, impressiones muscularis pallii 

 sinu magno. 



Shell ovate, convex, very thick, transversely wrinkled, rounded at both extremities, but 

 slightly attenuated at the posterior end, color dingy white and chalky, tooth robust, its inner 

 face smooth and rounded, its outer face divided near the posterior side by a deep furrow, and 

 the anterior edge turned up in shape like a tooth, anterior muscular impression oval, posterior 

 quadrangular ; the pallial impression very profound. 



Habitat, Volcano Bay, Island of Tedo. 



This shell is very similar to the Mya arenaria, but differs in the pallial impressions, which 

 are much more profound, the tooth more thickened, a deep notch on its posterior, and an 

 elevation on the anterior side, and the whole shell much more ponderous and incrassated. 



PSAMMOBIA OLIVACEA. 



Plate 1, figs. 8, 9. 



Testa ovata, tenui, violacea olivaceo-brunnea, striis concentricis, valva dextra planiuscula, 

 sinistra subventricosa, intus violacea. 



Shell ovate, thin, purple, covered with a shining olive epidermis, concentric strias ; right 

 valve nearly plane, but the other is somewhat ventricose, radiated with two white rays ; within 

 violet. 



Habitat, Bay of Yedo. 



The two rays are on the posterior slope ; the shell is about one inch long. 



CYTHEREA MERETREX. 



Plate ?, figs. 1, 2. 



Cytherea testa ponderosa, ovali subtrigona, lsevi alba postice cterulea, prope umbones vel omnino 

 angulatim fusco-maculata ; margine ventrali subinflato ; latere postico vix angulato, subelon- 

 gato, ad terminum subacuto ; lunula magna indistincta ; ligamento magno. 



Habitat, Canton river, China. 



Cytherea meretrix, (Linn.) 



Mr. Sowerby, in his monograph of the genus Cytherea, remarks that Lamarck has made nine 

 species of this shell and its varieties on the mere ground of variations in color. 



1 found upwards of five hundred of these shells in the collection of all colors and sizes, and 

 yet they run so one into the other that it is not easy to say where one species stops and another 

 commences. 



I have only been able to identify the four species that have been figured, and which I trust 

 will tend to elucidate this group of shells more fully. 



