Oysters and Scallops 87 



from all the other species in the inequality of its 

 valves, the lower being very convex outside, whilst 

 the upper is flat with a slight concavity towards the 

 beak. This upper valve is also smaller than the 

 lower, so that the lower margins do not meet. The 

 shell is thick and solid, ornamented and strengthened 

 by about 15 broad ribs, which are themselves corru- 

 gated. The lower valve is white suffused with pink 

 and pale yellow, but the upper valve has the ribs 

 dark red, and the intervening channels brown, the 

 whole colour paling away to the beak. The animal 

 is pink or red, the mantle marbled with brown and 

 white. There are from 30 to 35 large unequal 

 ocelli in two series, greenish or dark blue. The 

 young ones spin a byssus and suspend themselves by 

 it, but before they have become adult they appear to 

 have lost this power, or to have learned that their 

 shells have acquired sufficient weight and solidity to 

 resist movements of the lower waters. It occurs 

 generally around our islands in water of from 7 to 

 80 fathoms. The saucer-like lower valve has lono- 

 done duty as a drinking vessel. 



Closel}^ related to the Scallops are the File-shells 

 (Lima), so-called on account of the rasp-like character 

 of the shell sculpture. The valves of the shell are 

 uniform and always white, and the mantle is not 

 ornamented with prominent ocelli at the margins. 

 But though not well developed and conspicuous they 

 are there, and to make up for their deficiency the 

 tentacles which fringe the mantle are exceedingly 

 long and numerous, and wave about like the tentacles 

 of the sea-anemones. During early life the File- 

 shells flit through the water like the Scallops. The 



