Heart-Cockle and Fresh-water Cockle 97 



Interior of Heart-Cockle 



strange situation of the siphons is explained by the 

 habit of the Heart-Cockle : by means of the foot the 

 shell is embedded, beaks first, in 

 the slope of a muddy bank, so 

 that only the lower margin of 

 the shell with siphons is ex- 

 posed. It is a local shell, and 

 its distribution is almost con- 

 fined to Devon, Cornwall, the 

 west coast of Scotland, and the 

 south and east coasts of Ireland. 



The Northern Lucina {Lucina horecdis) is also an 

 almost round shell viewed from the side, but from 

 either end it is seen to be a much 

 flatter shell than the preceding. Its 

 whiteness is hidden by a yellow-brown 

 epidermis, and its surface is relieved 

 by a series of low but sharply cut 

 concentric ridges. The pointed beaks, 

 in spite of their small size, are tolerably 

 distinct. The hinge-teeth are two strong cardinals 

 with a long lateral on each side of the beak. The 

 interior margins are smooth and bevelled. The 

 animal is white, with short thick lips and extremely 

 short siphons. The long slender foot emerges from 

 the shell at about the centre of the lower maro-in, and 

 serves chiefly as an anchor to moor it to the gravel 

 and sand upon which it lies all round these islands. 

 from extreme low water to upwards of 100 fathoms. 

 There is a second species — the Prickly Lucina (Z. 

 spiiiifera) — which is of more local occurrence. The 

 shell is more triangular than the last named, the 

 epidermis of a much paler tint, the beaks less 



Northern Lucina 



