VARIETIES OF OYSTERS. 147 



latter. It appeared to me that, having been accidentally 

 detached from oysters in an adjoining bed, to which they 

 were originally affixed, and being thus deprived of their 

 plugs, as well as of the power to make new ones, they 

 filled up the openings with a shelly substitute, for the sake 

 of protection against starfishes and other enemies. Having 

 lost their own plugs, they were well* satisfied by being 

 securely moored to the bed by the strong cables of their 

 friendly neighbours, the mussels. 



I dredged a specimen of the variety "squamula" off 

 Croulin Island, Skye, which was free, but had the orifice 

 completely closed in the same way as the Welsh examples. 

 The A. tubularis of Turton is a young specimen of the 

 same variety, in which the orifice had only been partially 

 closed. Old Martin Lister was well acquainted with the 

 typical form, and gave an excellent figure of it in his 

 " Historia Conchyliorum." 



2. ANOMIA PATELLIFORMIS. Linne. 



Anomia Patelliformis. Linnaeus, Syst. Nat., p. 1151. 

 Forbes and Hanley, 2. p. 334. 



BODY resembling that of A. ephippium, but the colour 

 is deeper : mantle thinner : cirri of unequal length and size, 

 and capable of considerable extension, some of them 

 being a quarter of an inch long ; they are minutely and 

 closely ringed, and a dusky line runs down the middle of 

 each. No other part of the animal is visible outside. 



SHELL round or sometimes longitudinally oval, usually 

 flattened, thin, rather glossy towards the beak, but elsewhere 

 of a dull appearance : sculpture, fine and close-set imbri- 

 cated scales, and 20-30 blunt ribs, which radiate from the 

 beak in every direction towards the margins, in a wavy 



