56 



SHELL GALLEEY. 



the life-history of a species of each being illustrated by specimens, 

 figures, and models. In case 2 the Eound-Worms are illustrated 

 by models of Trichina, and the anatomical structure of various 

 other kinds is shown by the aid of diagrams. Case 3 contains 

 the free-living terrestrial and marine Worms, the Leeches, and 

 Gephyreans. Case 4 is devoted to specimens of Echinoderms 



Fig. 28. — Tbb Common Whelk (Buocinum undatum), a Gastropod Mollusc, 

 a, siphon; 6, foot; c, tentacles; (J, eyes; tJ, operculnin. 



Fio. 29, — Left Valve oi' the Giant Clam (Tridacna gigantea), 



a Bivalve Mollusc. 



(Length, 36 inches ; weight, 154 lbs. ; weight of the two valves, 310 lbs.) 



preserved in spirit, especially Holothurians, such as Trepangs 

 or Sea-Cucumbers, the Beche-de-Mer of the French. 

 Shell Gallery. V. A large gallery is devoted to the extensive group of 

 Shell-fish or Molliisca, the exhibition of which is, however, 

 mainly restricted to their shells. In some cases the form of 

 the " animal " itself is shown either by specimens in spirit or 

 by means of models. 



