8 SHELL GALLERY. 



Class III. GASTROPODA (continued). Pages 



Subclass II. OPISTHOBRANCHIATA. 



Order 1. Tectibranchiata : Bubble-shells, Sea-Hares, 



Umbrella-shells 27, 28 



2. Nudibranchiata : Sea-Lemons (Boris), &c. . . 28 



Subclass III. NUCLEOBRANCHIATA Cor HETEROPODA). 



Firolas, Carinarias, Atlantas 29 



Subclass IV. PULMONATA. 



Order 1. Stylommatophora : Slugs, Snails 30, 31 



2. Basommatophora: Water-Snails, False Limpets 31,32 



Class IV. SCAPHOPODA : Tooth-shells (Dentalium) 32 



Class V. PELECYPODA (or L AMELLIBRANCHIATA) . 



Order 1. Siphoniba : Clam-shells, Cockles, Tellens, 

 Wedge-shells, Gapers, Razor-shells, Pid- 



docks, Wateringpot-shells, &c 34-40 



2. Asiphonida : Oysters, Scallops, Pearl-Oysters, 



Mussels, Arks, River-Mussels, &c 40-46 



CEPHALOPODA*. 



[Case 1 This Class includes the Octopus, Cuttlefish, Squid, Spirula, the 

 a-d.j Paper and Pearly Nautilus. The body of the animal consists of a 

 muscular sac, in the cavity of which the viscera are placed. In 

 front of the body projects the head, which, in species belonging to 

 the two-gilled section of the Class, is surrounded by eight or ten 

 fleshy arms. A wide aperture below the head admits the water to 

 the gills or branchise, which are situated in the interior of the sac, 

 whilst a short tube, the so-called funnel or siphuncle, projects from 

 the opening of the mantle — the water and various excretions being 

 expelled through this tube, especially also an ink-like fluid, which 

 is discharged by all Cephalopods (except Nautilus) when disturbed, 

 in order to darken the water and thus escape their enemies. The 

 centre of the head, between the base of the arms, is occupied by 

 the mouth, which is armed with two horny or calcareous jaws, 

 similar to the beak of a parrot. The two large eyes are placed on 



* From the Greek : kephale, head, and potts, foot. 



