CARDIUM. 293 



specimens resemble punctures : colour milk-white, with occa- 

 sionally a very faint prismatic hue : margins rounded on all 

 sides except behind, where there is a gradual slope towards 

 the posterior end, which in the young is indistinctly angular : 

 beaks very small, glossy, turning towards the anterior side ; 

 lunule-shaped depression rather long and deep : ligament 

 short, yellowish-brown, projecting above the dorsal line : 

 hinge-line curved : hinge-plate narrow and sharp, occupying 

 between a third and a fourth of the circumference : teeth, in 

 the right valve one double cardinal (the plates or lobes of which 

 are of unequal size), with a short triangular lateral on the 

 anterior side and a small sunken laminar lateral on the pos- 

 terior side ; in the left valve are corresponding cardinals and 

 laterals, the latter on the anterior side being double : inside 

 polished and slightly nacreous, fluted in every part, owing to 

 the concavity of the outside ribs, the flutings having broad and 

 truncate terminations : scars slight and usually indistinct. 

 L. 0-4. B. 0-4. 



Habitat : Fine sand in 5-100 fathoms, west of Scot- 

 land and Moray Firth, Shetland, and all the Irish coasts ; 

 Mr. M'Andrew has dredged it sixty miles N.N.W. of 

 the Land's End in 50 fathoms. It is a local species. 

 According to Geikie it has been found by Mr. Richmond 

 in the glacial deposits at Bute. It inhabits the seas of 

 Scandinavia and the western coasts of the Baltic, at 

 depths varying from 10 to 130 fathoms. Philippi dis- 

 covered a recent single valve at Panormi, and many in a 

 fossil state at Palermo and Tarenti ; and M. Martin has 

 taken it alive in the Gulf of Lyons. 



Clark thought that this might be a variety of C. edule. 

 It is, however, a much more delicate shell ; its length 

 is greater in proportion to its breadth, and its contour 

 is more oblique; the transverse scales are arched or 

 vaulted, instead of straight ; the interstices of the ribs 

 are minutely striated or punctured ; and the inside is 

 fluted throughout, and not towards the edge only, and 

 the extremities of these internal grooves are truncate or 

 blunt, being in C. edule sharply pointed. 



