CONCHOLOGY. 17 



CLASS II. 



CIRRHIPEDES. 



HAS BUT ONE FAMILY. 



CiRRHiPEDEs. Ten genera. 



Lamarck divided the Lepas of Linnaeus into the various 

 genera which compose this family. The term lepas is de- 

 rived from the Greek w^ord Xeirag, a rock, alluding to its 

 custom of adhering to rocks and marine bodies. The shell 

 often varies in shape, covering, and colouring ; it is gener- 

 ally conical, but sometimes hemispherical; some of the valves 

 are placed perpendicularly on a base, broad at the lower 

 margin and tapering towards the summit, which is closed 

 by small horizontal valves forming the operculum. The 

 number of valves is indefinite, from four to twenty-four ; but 

 all are diversified with striae, ridges, and grooves. The striae 

 are mostly transverse, and the ridges longitudinal. 



The valves which compose the operculum or lid vary in 

 shape, and are in number two, three, four, or more ; they are 

 generally attached to a ligament. 



They are seldom, if ever, found detached, but adhere in 

 groups to rocks, shells, anchors, marine animals, &c. Those 

 that fix themselves to ships are generally called barnacles ; 

 they rapidly increase in size and number, do great damage, 

 and greatly impede the progress of the vessel. Some of 

 this family are affixed at the base of the shell to other sub- 

 stances, and are therefore called sessile ; others are attached 

 to a fleshy peduncle or stem, and are said to be pedunculated. 

 The peduncle or stem, proceeding from the base of the shell 

 to the substance which sustains it, is sometimes smooth, fine 



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