184 GOIUGBYLI A— DITHYRA.il. 



Turton, Conch. Diet. p. 29. 



Chemnitz, vi. p. 165, tab. 15, fig. 158. 

 Pectunculus orbicularis. Lister, Conch, tab. 324, fig. 161. 

 Cardium ciliare. Linn. Syst. &c. The youug shell. 

 Mus. nost. On most sandy coasts. 



Shell two inches in diameter, a little oblique, of a brown or whi- 

 tish color, clothed with numerous sharp white spines which curve 

 towards the cartilage side ; those on the opposite side thicker and 

 more obtuse. 



The young of this species, and of the Cardium aculeatum, are iu 

 many respects so similar, that it is hardly possible to fix with any 

 decision, which of them should be considered as the Cardium ciliare 

 of Linne and subsequent authors. 



Both of them are thin and brittle, and have the sjiines lance- 

 shaped or longitudinally dilated at the base. 



The young of Cardium echinatum are entirely white, with the 

 grooves regularly striate transversely. They are abundant in Dublin 

 bay, where the Cardium aculeatum has never been found to inhabit. 



The young of Cardium aculeatum are extremely fragile and trans- 

 parent, more dilated at the sides from the beaks, of a fine glossy 

 fawn-color, and irregularly striate in the grooves : they are of rare 

 occurrence, but found occasionally on the sands at Paington. It is 

 figured in Chemnitz, vi. tab. 17. fig. 171, 172. 



The young of Cardium tuberculatum are of a stronger consistence, 

 of a deeper chocolate brown with white blotches or rays, and cloth- 

 ed with rather obtuse raised tubercles. 



