58 



POPULAR CONCHOLOGY. 



9. GtASTROCELENA. — Shell equivalve, in- 

 equilateral, gaping very widely on one side, 



united by a ligament, and having in the inte- 

 rior a small spoon-shaped curvature. The tube 

 differs from that of Fistulana in being nearly 

 divided into two. Animal having two tubes 

 and a thick short foot. — 3 recent species. 



The Gastrochcena penetrates and makes its 

 abode in hard substances: it seldom exceeds 

 half an inch in length, and inhabits the coasts 

 of Great Britain, the Isle of France, and Ame- 

 rica. G. modiolina is the English species. 



10. Teredo. — Shell, valves gaping, having 

 a long recurved tooth under the boss of each, 

 external and attached to the animal, not to the 

 tube, which is long, irregular, and open at both 

 ends. Animal long, worm-shaped, having two 

 little tubes. — 2 species, recent. 



The Teredo is almost the only mollusc which 

 is to any extent injurious to mankind, and this 



