GENUS CHTHAMALUS. 449 



often so completely masked, owing to its varying shape, 

 its obliterated sutures, its deeply disintegrated and punc- 

 tured surface, and by the corroded condition of its opercular 

 valves, that I have found this species, in the collections of 

 naturalists who have attended to cirripedes, arranged actually 

 on the same tablet, mingled with specimens of Balanus 

 balanoides. I have myself several times found it less 

 troublesome to discriminate these two genera by the in- 

 cluded animal's body than by the shell,* though the latter, 

 when well preserved and developed, possesses such ob- 

 viously well-marked characters : the same thing has occurred 

 to me with some of the other species. 



General Appearance. — The shell is generally depressed, 

 but sometimes, when growing in groups, cylindrical. The 

 surface is either smooth or longitudinally folded; and, as 

 already stated, very apt to be deeply disintegrated. The 

 radii, when developed, are narrow, with their summits 

 oblique and rounded ; but they are often quite absent, and 

 sometimes even the sutures are almost obliterated. The 

 rostrum and carina are of the same shape and size, and the 

 two lateral compartments on each side are of nearly equal 

 breadths. The orifice is generally sub-rhomboiclal, being 

 widest towards the carinal, instead of towards the rostral 

 end, as is usual in Balanus : but in Chthamalus fssus the 

 orifice is narrow and elongated. The opercular valves have 

 their apices generally disintegrated and worn away, and are 

 then seen to be deeply locked together. The colour of the 

 shell is dirty white or dull purplish-red or brown ; but in 

 C. intertextus rich violet-purple. The species are small, not 

 often exceeding half an inch in basal diameter, with the 

 exception of C. Hembeli, of which I have seen a specimen 

 two and three quarters of an inch in diameter. 



Scuta. — These present no particular character, excepting 

 in most cases the large development of the articular ridge, 

 and sometimes the presence of a furrow above the articular 



* It will be found ultimately to save time and trouble, to soak for half an 

 hour in hot caustic potash, a specimen out of each group of shells to be 

 examined, and then well wash and brush the separated valves and compart- 

 ments ; this process has been followed by me with all the species here to be 

 described. 



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