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GENUS III. 

 SPHENOTROCHUS (M. Edw. & Haime). 



Turbinolia (Lamarck). 



Corattum simple, free, with no trace of adherence, 

 wedge-shaped, the superior extremity wider in all 

 directions than the inferior ; transversely elliptical. 



Columella, a single lamina, occupying the greater 

 axis of the ccdice : its upper margin flexuous and 

 bilobate. 



Palules entirely wanting. 



Plates extending to the columella, or meeting in the 

 centre of the visceral chamber ; broad, slightly salient, 

 forming three cycles, and six systems. 



Bils broad, not very prominent, in general crisped, 

 or represented by a series of papillous tubercles. 



ANALYSIS OF BRITISH SPECIES. 



Corallum uniformly diminishing downward ; ribs smooth . Macandrewanus. 

 Corallurn pedicellate, with swelling nodes; ribs crisped . Wrightii. 



Y 2 



