CHTHAftALUS HEMBELI. 405 



from the West Indies, but it was the variety which so com- 

 monly adheres to ships' bottoms. This variety often arrives 

 alive in British ports ; and I have seen a specimen picked 

 up dead on the beach near Dublin. 



6. Chthamalus Hembeli. Tab. 18, fig. 5 a — 5 d 3 e. 



Euraphia Hbmbeli. Conrad. Journal Acad. Nat. Sc. Philadelphia, 



vol. 7, 1834, PI. 20, fig. 6. 



Shell dull reddish-purple: sutures, when not obliterated, 

 formed by interlocking teeth : basis sometimes rendered cal- 

 careous by the inflexion of the parietes : scutum ivith two or 

 three fur roios extending down the middle of the valve. 



Rab. — California, near S. Diego, according to Conrad. Mus. Brit., Cuming. 



I have seen five, old, large specimens, from an unknown 

 locality, with their whole surfaces deeply corroded, and 

 with most of the sutures obliterated; and three separated 

 valves of a young specimen. From these materials, imper- 

 fect as they are, I feel no hesitation in identifying this 

 species with the Euraphia Ilembeli of Conrad, which is re- 

 markable in several respects, and especially from being 

 gigantic in size, compared to other members of its sub- 

 family. 



General Appearance and Structure of Shell. — The young specimen 

 (fig. 5 b y about '7 of an inch in basal diameter) consists only of the 

 carina, and the two lateral compartments ; but these, as far as I can 

 judge, resemble the specimen figured and described by Conrad, which 

 was two inches in diameter. Shell depressed, spreading, surface mo- 

 derately smooth, covered by brownish membrane: shell itsejf pale dull 

 reddish-purple. The radii are not very narrow 7 , with their summits 

 rounded and very oblique : their edges are toothed, and their external 

 surfaces are transversely ribbed, in correspondence with the interlocking 

 points of the sutures. On the internal surface, the toothed suture is 

 not visible, except near the base of the shell, owing to the overlapping 

 of the alee. The alee have oblique summits, which are slightly notched 

 owing to the upturned prominent lines of growth. The parietes are 

 thick ; their basal internal surfaces are rugged, with slightly branching 

 ridges. 



The old specimens (fig. j a) are so much corroded that not a particle of 



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