168 



Examples, Mytilus (Mussel), f The " foot " small. 

 Lives (in colonies) attached by a byssus 

 of threads. Marine. See page 175. 



Meleagrina, syn. Margaritifera (Pearl Oys- 

 ter). Marine. 



Pecten (Scallop, or Clam). The " foot '* 

 not locomotor, but used for spinning 

 the byssus. Marine. 



Lima. Edges of mantle have very long 

 filaments. Swims freely by flapping its 

 valves, or attaches itself by the byssus 

 and forms a large nest of fragments of 

 shell, stone, coral, etc. Marine. 



Ostrea (Edible Oyster). Without a " foot " 

 and a byssus. Hermaphrodite. 



Anodonta (Freshwater Mussel). The "foot" 

 large and wedge-shaped. Without a 

 byssus. Sexes separate. A Glochidium 

 larva. 



Cardium (Cockle). Siphons short. The 

 long and bent " foot " is used for leaping. 



Mya (Gaper). Siphons long. Marine. 



Pholas (Piddock). A boring Mollusc ; 

 bores in rock, shale, etc. Marine 

 (littoral). 



Teredo (Ship-worm). Body long and worm- 

 like, and more or less enclosed in a 

 thin shelly tube continuous with the 

 small shell. A destructive wood-borer. 



Class SEPHONOPODA or CEPHALOPODA. Bilaterally symmetrical. 

 The head distinct and surrounded by prehensile " arms " with 

 suckers. An odontophore with a radula, and two jaws. The front 

 portion of the " foot " forms the sucker-bearing " arms," and the 

 hind portion forms the sii>hon or funnel through which water is 

 expelled from the mantle-cavity. The ganglia are massed together 

 and protected by an internal cartilaginous " skull." Eyes, corlome, 

 and vascular system are well developed. Sexes separate. Develop- 

 ment direct. Free-swimming and marine. 



Examples, Octopus. Body bag-like. Head large. 

 Eight long and webbed " arms " each 

 with, two rows of suckers. Two gills. 

 Shell absent. 



