163 



costa interna gracili, elongata, laetea. Long. 10 ; alt. 6 ; lat. 3 

 millim. 



Only one valve was obtained, evidently more equilateral, thin, and 

 obtuse posteriorly than any described species. 



Saxicava flaccida. T. tenuis, subnacrea, multiformis plerumque 

 subquadrata varie distorta, concentrice undulata, epidermide tenui 

 ochracea rugosa induta ; umbouibus terminalibus, tumidis ; declivitate 

 post-umbonali carinata interdum spinulosa : cavositas subnacrea ; 

 cardinis dente valido elongato, uncinato. Long. 20 ; alt. 13 ; lat. 10 

 millim. Inhabits Hong Kong and Simon's Bay. W. S. 



The strong cardinal tooth and the semi-pearly structure are al- 

 together unusual for this genus. It would come under Hiatella or 

 Rhomboides, which are now regarded as variations of Saxicava. I 

 cannot distinctly make out a pallial impression. The animal has a bys- 

 sus. Perhaps these shells have been confounded with Sax. rugosa, 

 which is said to come from Cape of Good Hope, China, &c. I am 

 by no means certain that the shells from the two localities which 

 I have had under inspection are the same. Those from the latter 

 locality are certainly much the smallest. 



Cryptomya truncata. T. tenuis, alba, rotundato-ovata, postice 

 oblique truncata ; umbonibus submedianis, parvis ; valvii (dextra) 

 tumidii, fastigio acuto ab umbone ad angulum postero-ventralem 

 tendente divisa ; area antica striis concentricis et postice striis radian- 

 tibus ornata ; area postero-dorsali triangulari eburnea, sulco radiante 

 partita, et striis lamellosis concentricis insculpta. Long. 18; alt. 13; 

 lat. 10 millim. Inhabits the China Sea, lat. 24° N. W. S. 



The cartilage pit is oblong, narrow, somewhat oblique, and nearly 

 appressed against the margin ; behind it is a protrusion of the margin 

 almost like a lateral tooth. Only one valve having been examined, 

 the generic place is not fully settled. 



Panop^ea fragilis. T. elliptica, tenuis, fragilis, livido-albida, 

 concentrice undulata ; umbonibus submedianis ; extremitate antica 

 obtuse rotundata ; extrem. postica subtruneata ; cardine debili ; apo- 

 physi ligamentali brevi ; dente elongato ; margine dorsali ad basin 

 dentis fissurata. Long. 2 ; alt. 1,5; lat. 1 inch. Inhabits Hakodadi 

 Bay. W. S. 



Remarkable for its fragile structure and waved surface, like some 

 of the Thracia?, or Mactracea?, or still more like Pholadomya. 



Panop^ea generosa. Several specimens were obtained at 

 Awatska Bay, Kamtschatka, which are probably this species ; but 

 the beaks are much more anterior, the posterior truncation is much 

 more oblique and in a different direction, and the gape is much less 

 than in the specimen originally described. They have also a double 

 structure, — an inner porcellanous layer, and a more earthy, some- 



