56 
SHELL GALLERY. 
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. — The Common Whelk (Buocinum undatum), a Gastropod Mollusc, 
a, siphon ; 6, foot ; c, tentacles ; d, eyes ; e, operculum. 
Fig. 29. — Left Valve of 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 Mollusc A, 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. 
