Heart-Cockle and Fresh-water Cockle 105 



The shell is white with a tendency towards a 

 yellowish tint, which is the hue of the opalescent 

 epidermis. An enlarged figure of the 

 hinge-teeth is given ; tliey are more 

 highly developed than in squainosiun. 

 The foot is more distinctly blue, flecked shining coin-siieii 

 with white, and the siphon is placed in ^" enlarge mge 

 front instead of behind. It occurs sparingly on 

 all our coasts where there is coarse sand, between 

 10 and 90 fathoms. The form sometimes described 



as a separate species under the name of the 



1^^ Convex Coin-shell (L. convexiiin) appears to 



Convex ^^ ^ Variety {convexa) of L. nitidmn. It is 



^°'"- distinguished by the shell being slightly 



more convex, and marked all over with coarser 

 pits than those found only round the beaks in the 

 type. 



The Furrowed Coin-shell (L. sidcatulum) is almost 

 circular in outline and flattened ; its substance tliin 

 and almost transparent, like that of L. sqiiamosuin, 

 but instead of the pit marks we have here a numerous 

 series of broad concentric ribs covering the surface. 

 The cardinal tooth in the left valve is strong and 

 erect, whilst the corresponding one in the right is 

 very small. The length of the shell is only about 

 one-twentieth of an inch. It appears to be a southern 

 form, and has been found in the Channel Islands 

 among corallines below the lowest tide-marks. Clark's 

 Coin-shell (L. clarkice) is another minute species, but 

 of more yellow tint than the last, streaked with fine 

 white lines that radiate from the beak. Instead of 

 the ribs of L. sulcatuhwi, the sculpture here consists 

 of numerous fine concentric grooves. The outline is 



