MULTI VALVES. LEPAS. 17 



ing (with few exceptions) of a more or less conical shape, 

 which is acquired by a number of valves being placed 

 perpendicularly on a base, broad at the lower margin, 

 and gradually tapering towards the summit, which is clos- 

 ed by other smaller valves, placed horizontally, thereby 

 serving as a lid or covering to the animal within. 



The perpendicular valves are capable of no motion ; 

 whereas, on the contrary, the horizontal ones are movea- 

 ble at the pleasure of the animal ; who, through their me- 

 dium, performs those fiuictions which are necessary to its 

 existence. 



The Lepas is never found independent or isolated, 

 as most other shells are; on the contrary, all its species 

 are known to affix or attach themselves by their base 

 or fleshy stalk to other bodies; they adhere in clus- 

 ters or groups, to rocks, coral reefs, ships' bottoms, 

 and shell-fish: even fish themselves, while swimming, 

 are not exempt from their encroachments, for instance, 

 the whale, and others, are frequently found laden with 

 them; and even tortoises are often encrusted with groups 

 of the Lepas species. It would therefore appear, that 

 the genus is merely capable of motion, and in case of 

 their being transported from one place to another, it is 

 to the exertion of other bodies that they must be indebted 

 for their migration. 



The exterior of the shell is often varied in form, cover- 

 ing, and coloring; the usual outline is conical; in others, 

 it resembles a pyramid, and, in some instances, is para- 

 bolical, and even hemispherical: the Lepas diadema 

 partakes of the latter form, and somewhat resembles a 

 divided globe. The number of valves which constitute 

 the shell is often very indefinite, their usual amount is 

 six; but the Lepas palmipes has sometimes only four; 

 c 



