TROCHUS. 11 



small, ovate, outer lip thick, crenulated within ; columella toothed 

 at base, subtruncated. Type, C. conicu^ Gray. 



Section Odontotrochus Fischer. 



Shell conical, elevated ; periphery acutely carinated ; columella 

 toothed below, truncated. Type, C. chlorostomus Mke. 



Genus GAZA Watson, 1878. 

 Shell trochiforni, nacreous both on the surface and throughout ; 

 delicately sculptured, with a reversed lip thickened internally by a 

 nacreous callus ; the pillar twisted direct, in front angulated and 

 pointed, behind entirely parted from the lip, and in the umbilical 

 region spread out in a nacreous pad. ( Watson) Type, G. da?dala 

 Watson. Fiji Is. 



Subgenus Microgaza Dall. 1881. 

 Shell flattened, rotelliform, resembling a Gaza without reflected 

 lip or umbilical callus, brilliantly nacreous when fresh, and having 

 a distinctly scalariform umbilicus. (Dall) Type, M. rotella Dall. 



Barbados. 



Genus CALLOGAZA Dall, 1881. 

 Shell resembling Gaza Watson, but with the umbilical pad re- 

 flected only partly over the umbilicus ; the pillar straight, passing 

 without notch or mucronation into the reflected basal margin of the 

 aperture ; nacreous layer in this shell covered with a thin non- 

 nacreous layer, which appears to be covered by a delicate epider- 

 mis. (Dall) Type, C. superba Dall. 



Genus BEMBIX Watson, 1878. 



Shell conical, high, carinated, tumid on the base, umbilicated, 

 thin, nacreous, covered with a thin membranaceous epidermis. ( Wat- 

 son) Type, B. teola. Japan. 



Genus CHLOROSTOMA Swainson, 1840. 



Shell conical, umbilicate or imperforate, solid ; spire elevated or 

 depressed ; aperture oblique, subrhomboidal, the outer lip smooth 

 within ; columella arcuate, above continued in a callus over or half- 

 Avay around the umbilicus, which when oj^en shows one or more 

 spiral ribs inside ; base t)f columella with two or more denticles. 

 Type, C. argyrostomum Gmel. 



Chinese and Japanese Seas, W. Coast America, West Indies. 



