214 



TEE SEA SHORE 



throughout when extended ; and the gills, numbering either one or 

 two on each side, are large and thick. In all the members of this 

 family, as in the last, the pallial line of the shell is simple. None 

 of the shells are really common objects of our shores, since the 

 animals inhabit deep water, some of them moving about freely on 

 the bottom, while others moor themselves by means of a byssus. 



We shall take only one example of the family Galeomma 

 Turtoni the generic name of which means 'weasel eye.' This 

 pretty little mollusc may be found on our southern coasts, where it 

 often moors itself to the rocks or weeds by 

 means of its silken byssus ; or, having broken 

 itself away from its temporary place of rest, 

 creeps freely on the bottom by a long, flat- 

 tened foot, applied closely to the surface over 

 which it travels, and used much in the same 

 way as the broad foot of a snail or whelk, its 

 valves being all the time spread out nearly 

 in the same plane. 



The shell itself is oval, with central um- 

 bones, and is covered with a thick epidermis. 

 The mantle lobes are united behind, where 

 they form a single siphonal opening; and 

 the margins are double, with a row of eye- 

 like spots on the inner edge of each. 



The true Cockles, some few species of 



which are known to almost every one, constitute the family Cardiadce, 

 so called on account of the cordate or heart-shaped form of the 

 shell as viewed from the anterior or posterior side. The shell is 

 regular, or nearly so, and the valves, which are equal, are orna- 

 mented with prominent rays that run from the umbones to the 

 margin. The ligament is short, strong and prominent, and the 

 valves fit closely by the interlocking of their crenulated margins, 

 or gape slightly on the posterior side. There are two central teeth 

 in each valve, and a long lateral tooth both on the anterior and 

 posterior sides. The mantle lobes are open in front, with the 

 margins plaited, and the siphons, which are usually short, are 

 provided with a number of little tentacles. The foot is large and 

 powerful, and is usually curved into the form of a sickle. 



Although the general nature of the common edible cockle (Car- 

 dium edule) is so well known even to the inhabitants of inland 

 towns that a description may seem out of place here, yet it is pos- 



FIG. 145. Galeomma 

 Turtoni 



