CONCHY LrA—D/TjHF/i^. 45. 203 



Shell very irregular, sometimes growing to a large size, w'lien' 

 the beak, of the under valve becomes much elengated, and trans- 

 versely striate in the ligameatous cavity. 



OsTREA testd subrotundd vel ohlongd leviusculd parasiticd. parasitic*. 



vulva superiori convexd. 

 Shell roundish or oblong nearly smooth and fixed to other sub- 

 stances, with the upper valve convex. 



Tab. nost. 17. fig. 6 and 7, 

 Ostrea parasitica. Chemnitz, viii. p. 19, tab. 71, fig. 660. 



Turton, Conch. Diet. p. 134, fig. 8. 

 Ostrea orientalis. Dillwyn, Descript. Catal. p. 274. 

 Mtts. nost. On bivalves, crabs, and submarine substances. 



Shell from half an inch to two inches in diameter, very variable 

 in figure and substance, sometimes very thin and radiate witlj 

 black or brown, when attached to the Pecten opercularis: sonie'- 

 times thick, with the upper valve semicylindrically tumid^ and 

 the under valve conca;ve underneath, as if it had accommodated 

 its shape to a piece of stick of the size of the fore- finger, with the 

 beaks much incurved on one side and not extending beyond the 

 margin : the surface is nearly smooth, of a' greenish color with 

 occasionally some dark longitudinal marks ; inside perlacevusy 

 with fine crenulations on each side the hinge. 



A small variety is found fixed to Serpulse, the inside of old 

 Oyiter-shells, and sometimes in the cavities of rocks, with the 

 upper valve flat and a little scaly ; the under valve very concave 

 and hollow, especially under the hinge ; the beak of the concave 

 or under valve often much lengthened, an' evidence of age ; and 



