30 



Animal Life by the Sea-shore. 



mud. The two valves of the shell are connected by an elastic 

 ligament, the action of which is indirectl}' controlled by the 

 animal, becoming relaxed and causing the valves to gape after 

 death, when the muscles cease to function. As a typical marine 

 bivalve we may mention the Cockle {Cardiuni cditlc), so common 

 on sandy shores, especiallj' near estuaries, \vhere the salinity 

 of the sea is reduced by an influx of fresh water. It usually lives 

 just buried belov/ the surface of the sand, or a mingling of sand 

 and mud, and, in order to keep up a respiratory current, the 

 mantle is produced into two tubular structures which project 

 from the shell and function as inlialent and exhalent siphons. 

 The Cockle burrows by means of the long bent foot (Fig. 30) 

 which is also used to perform peculiar leapmg movements, for this 

 Mollusc is remarkably active at times and able to jump con- 

 siderable distances. 



The Clam, or Gaper {Mya tnmcata), lives much m the same 

 situations as the Cockle, being, however, a more sta\'-at-home 

 animal, remaining embedded, often a foot deep, in sandy mud ; 

 in relation with this mode of existence, the united siphons are 

 extremely long (Fig. 29). The valves of the shell chffcr from those 

 of the Cockle in being oval and devoid of radial ridges. The 

 oval shell is characteristic of many of the marine Pdecypods, 



riG. 20. CLA5T, WITH ARROWS SHOWING INHALENT AND 



IIXHALENT ORIFICES OF SIPHON. [After Wt,n,-hdiai,1 .) 



the species of wliich are somewhat difficult tn define briefly ; 

 two are here figured (Fig. 31). Tellina balihica is noticeable on 

 account of its delicate colouring ; the valves are white, pale 

 pink, or yellow externall}', bright pink internal]}'. Another pretty 

 shell to be found commonly on the beach is Doiiax veiiusliis. 

 of more elongate shape and of a violet colour in the interior. 

 Cyprina islandica is a larger and more massi^'o and convex 

 shell, of brown colour. 



The extraordinar^'-looking Razor shells {Soleu cnsis and 

 5. siliqiw) differ strikingly' from our other litt(Dral bivah'es 

 in their greatl)' elongated form, reaching a length of 



