Mollusca in the Collection of the Zoological Society. 365 



*ASTARTE CRASSIDENS. 



A. testd suborbiculari, crassd, obsolete radiatim sulcatd ; antich brevis- 

 simd ; umbonibus antice productis ; marginibus infernis crenatis ; 

 cardinelato, dente centraliin valvd altera maximo ; long. l-j%, lat. 

 i-2-, alt. m, poll 

 Hab. in Oceano Arctico. 



A single specimen of this fine species of Astarte was obtained off Icy 

 Cape by Lieut. Belcher. Its epidermis is thick and dark coloured, but 

 it is much eroded around the umbones. The shell is of a dirty white 

 colour, except the center within, where it is tinged with dull reddish 

 purple. The edges of the very broad tooth in the hinge of the right 

 valve are irregularly sculptured. The internal marginal crenations are 

 very wide, and have almost the appearance of low embrasures. In Mr. 

 Bland's collection. 



Astarte lactea. 



ji. testd obovatd, compressd, antlch breviore ; margine dorsali postico 

 depresso ; intus lactea, marginibus integerrimis ; long. \-^q, lat. -^■^, 

 alt. i-i^^, poll. 

 Hab. in Oceano Arctico. 



The outer surface is rather dull, it has a thick, dark coloured epider- 

 mis, and is distinctly marked with the concentric lines of growth. From 

 Icy Cape. 



Arca grandis. 



ji. testd obliquk subquadratd, crassd^ albd, radiatim costatd, loevi, cos- 

 tis rotundatis, anticis crenulatis, reliquis muticis, epidermide co- 

 riaced ; long. 4-^%, lat. S^V* ('dt. 3yVj poll. 

 Hab. 



The largest species of Arca we remember to have seen, growing even 

 to a larger size than".^. senilis, which it also resembles very much ; it is, 

 however, longer, end the number of ribs greater. 



Arca gradata. 

 ./?. testd oblongd, postice angulatd ; costis concentricis, radiatim imbri- 



VOL. IV. B B 



