IVedge-shellSy Venus-shells^ and Cockles 125 



concentric bands of deeper tint than the ground colour. 



The animal is very agile, of a purplish red or yellow 



colour ; the siphons are pale 



orange, and not more than 



half an inch in length. It 



is plentiful at low water in 



most sandy bays. The r. ^ . ., ^ 



«^ •^ Banded Wedge-shell 



Polished Wedge - shell (D. 



l^olitus) may be at once distinguished from the 

 preceding by the absence of the milling along the 

 inner margin of the valves. The 

 colour is chestnut-brown varying 

 towards olive, with a broad cream- 

 coloured ray and some marbling 



Polished Wedge-shell ^^ ^j^^ ^^^^^ ^.^^_ j^ burrOWS iu 



sand at extreme low water and a few fathoms 

 below it, chiefly on the coasts of Devon, Corn- 

 wall, and the Channel Islands. The Abrupt 

 Wedge-shell {D. trunculus) has been taken occasion- 

 ally on our southern shores. It is larger than the 

 Banded Wedge-shell, and may be distinguished from 

 it by being more acutely triangular, the striations 

 more delicate, and the inner edge not milled beneath 

 the hinge-ligament. Further, the hinder part of the 

 shell does not slope gradually to a point, but abruptly 

 as though cut off*. 



The Trough - shells {Mactra) are represented by 

 five or six species. The shells are triangular-oval, 

 swollen, with a slight gape behind. There are two 

 erect diverging cardinals, and large plate-like laterals 

 on each side of them — two in the right, one in the 

 left valve. These lateral teeth have their edp^es 

 milled in M. elliptica, M. solida, and 71/. sub- 



