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GENUS III. 
SPIIENOTROCHUS (M. Edw. & Haime). 
Turhinolia (Lajiarck), 
CorciUum 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 calice : its upper margin flexiioiis and 
bilobate. 
Paliiles 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. 
Pihs broad, not very prominent, in general crisped, 
or represented by a series of papillous tubercles. 
ANALYSIS OF BRITISH SPECIES. 
Comllum uniformly dimiuisliing downward ; ribs smooth . Macandrewanm. 
Corallurn pedicellate, with swelling nodes ; ribs crisped . Wrighlii. 
T 2 
