Mollusca in the Collection of the Zoolofjical Society. 365 



*ASTARTE CRASSIDENS. 



Jl. testd suborhiculari, crassd, obsoleU) radiatim salcatd ; antici brevis- 

 simd ; iimbonibus antia) productis ; marcjinibus internis crenatii ; 

 car dine lata, dente centraliin valvd alterd maximo ; loiuj, 1,"^, lat. 

 \l, alt. l[i, poll. 

 Hub. 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. 



./?. testd obovatd, compressd, antlct} breviure ; maryine dorsali postico 

 depresso ; intus laded, manjinibus integer rimis; long. 1,%, lat. -^-jj, 

 alt. 1^*0, 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. 



.^. testd obliquh subquadratd, crassd, albd, radiatim costatd, Icsvi, cos- 

 tis rotundatls, anticis creaulatis, reliquis muticis, epidermide co- 

 riaced; long. 4^'^, lat. 3/^, alt. 3-f'V, poll. 

 Hab. 



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

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

 however, longer, and the number of ribs greater. 



Arca gradata. 



A. testd oblongd, postice ungulald ; costis concentricis, radiatim imbri- 

 VoL. IV. u B 



