42 
SHELL GALLERY. 
forming some of the most attractive groups. The two rows of cases 
on the left contain the land-shells, Bivalves, and Cephalopods. 
The Cockles, Oysters, Clams, Piddocks, Teredos, Scallops, and 
Ark-Shells represent some of the principal types of Bivalves, 
so called on account of their shells being formed of two pieces 
or valves. A Giant Clam (fig. 15), on the floor of the gallery. 
Fig. 13.— a Stone-Lily, the Larval, or Pentacrinoid stage of 
Anledon rosacea, a, arinB ; h, basals ; r, radials ; s, stalk. 
weighs 310 lbs. The Argonaut, the beautiful pearly Nautilus 
(fig. 16), the Octopus, Squids, and Cuttlefishes are the chief 
kinds of Cephalopods. 
In the same gallery are exhibited three other groups of marine 
organisms, respectively known as the Polyzoa, Brachiopoda, and 
