42 



Cases 198- 

 199. 



SHELL GALLERY. 



blematical. A fine series of these shells is exhibited in Gallery VIII., 

 wall-case 5, in the Geological Department. 



The Myiclcn, popularly known as " Gapers,^'' on account of their 

 valves being open at one or both ends, have the mantle united all 

 round, except where the small foot is protruded. The siphons are 



Fig. 34. 



Case 198. 



Cases 199- 

 201. 



British Gaper {Mya truncata). 



ft, foot ; h, siphon-sheatli ; c, exhalant siphon ; d, inhalaiit siphon ; e, umbones 

 or beaks ; /, anterior, g, posterior end of shell. 



very long, united almost to the ends, and covered with a coarse 

 wrinkled outer skin. They bury themselves in mud and sand at low- 

 water mark or in shallow water. The species are few in number, ard 

 chiefly from the shores of northern countries. Mya arenaria of our 

 own coasts is largely eaten in some parts of Europe and North America. 



The CorhulcB (Case 198) have one valve larger than the other 

 and are like little MycB, but the valves are almost closed and their 

 siphons are very short. 



Many of the Solenidm, or Razor-shells, possess very elongated 

 shells, and are remarkable for the great development of the foot, 



Fig. 35. 



British Eazor-shell (^Solen siliqua). 

 a, foot ; h, mantle ; c, inhalant siphon ; cl, exhalant siphon ; e, shell. 



which can be extended or contracted as may be required for boring 

 into sand. By means of this powerful foot the animals, when 



