18 MULTIVALVES. LEPAS. 



and other species possess the intermediate gradations of 

 number, as far as twenty-four, vvliich amount is not nn- 

 frcquent in the Lepas Polhcipes. — The valves, of what- 

 ever number they consist, are variously diversified with 

 striae, ridges, and grooves. 



The ridges are mostly longitudinal ; the striae, on the 

 iontrary, are transverse, and not unfrequently beset with 

 rough projections and acute spines, as is the case in the 

 Lepas spinosa. 



The color also differs considerably, though the most 

 usual complexion is of a blueish, purplish, or reddish cast, 

 intermixed with a whitish hue. However, some are pied 

 with black and green alternately, and others are of a 

 greyish-white, or dirty-yellow tint, as may be observed 

 in the Lepas mitella and others. 



The valves which compose the lid or operculum, often 

 vary in their number and shape; sometimes they only 

 consist of two, at others, of three and four, and not unfre- 

 quently of a far greater number. They are usually at- 

 tached to a ligament, and sometimes present a pointed or 

 acute form, while in other species they are perfectly blunt 

 or obtuse. 



The interior of many of this genus is a mere vacuum, 

 but in others it is either filled up with tubular pores, as 

 in the Lepas Porosa,or else is divided into separate com- 

 partments or chambers. 



Notwithstanding the great affinity which exists 

 throughout the Lepas tribe, yet there are a few excep- 

 tionable species, in which a resemblance is difficult to be 

 traced; as, for example, in the Lepas scalpellum, anser- 

 ifera, anatifera, and varieties emanating from them. 



These three species are closely allied to each other, but 

 exceedingly dissimilar to the rest of their genus, for the 



