36 CONCHOLOGIST’S COMPANION. 
and yet among the multifarious productions of nature, 
I think we shall hardly discover more extraordinary 
instances of that general system of compensation, 
which supplies the defects of one part, or organ, by 
the structure of another. 
The shells of this interesting genus present con- 
siderable variety in form and beauty, and are divided 
into seven classes or divisions, which are again 
subdivided. The first, and second, comprise the 
numerous varieties of Scallop shells, and are distin- 
guished from each other by the proportions of their 
ears. The surfaces are usually adorned with divergent 
ribs, variegated with beautiful colours, and delicate 
chequer-work, and are covered with undulated and 
transverse striz, which not unfrequently assume 
the appearance of elevated scales, as in the Im- 
bricated Oyster. But how, when inclosed in these 
floating citadels, can the inhabitants either swim 
upon the water or move on land? This appa-. 
rent inconvenience is fully compensated by their 
inherent strength and flexibility, and by the muscles 
with which they are supplied. They possess the 
faculty of leaping to a considerable distance by the 
sudden opening and closing of their valves; and 
hence they are elegantly denominated, butterflies of 
the ocean: as, when darting through the sparkling 
waves, and flitting rapidly from place to place, they 
