152 OYSTERS, AND ALL ABOUT THEM. 



which is thick and very strong, light-brown or horn colour, 

 and supported on each side by a short ligament of a dark 

 olive-green : hinge-line narrow and nearly straight : hinge- 

 plate thick : inside white and pearly ; lateral edges (especi- 

 ally of the flat valve), finely crenulated or notched on the 

 upper part : muscular scar obliquely transverse, pear-shaped 

 or slightly incurved above. Length 3, breadth 3*5. 



Var. i, parasitica. Shell much smaller, flatter, and 

 more glossy ; colour purplish or greenish-brown, with 

 streaks of a darker hue radiating from the beaks. 0. para- 

 sitica, Turt. Conch. Diet., p. 134, f. 8. 



Var. 2, hippopus. Shell large and extremely thick. 

 O. hippopus, Lam. An. sans Vert. 7, p. 219. 



Var. 3, deformis. Shell small, distorted, and often 

 nearly cylindrical. O. deformis, Lam. 1. c., p. 229. 



Var. 4, Rutupina. Shell small, transversely oval, and 

 of a regular shape. 



Var. 5, tincta. Shell flattened and attached in every 

 stage of growth ; inside of a rich purplish-brown or olive- 

 green ; hinge-margins strongly crenulated. 



HABITAT : 0-45 fathoms, on every part of our coast, 

 from Shetland to the Channel Isles, usually gregarious and 

 forming beds of various extent. Var. i, on shells, crabs, 

 and other substances, having rather a more southern dis- 

 tribution. When this variety is affixed to a ribbed scallop, 

 it adopts the markings of that shell, but it retains its own 

 colour. It appears to be the O. depressa of Philippi. Var. 

 2. In deep water and solitary. Var. 3. Occupying the 

 crevices of rocks, in the littoral and laminarian zones, and 

 called the " rock oyster." Some specimens resemble the 

 Gryphoca in shape. Var. 4. Coasts of Essex and North 



