110 



TURBO. 



A. Pillar margin of the aperture dilated^ im- 



perforate. (Plate XIX. fig. 4.) 



B. Solid^ imperforate, (fig. 5.) 



C. Solid, perforate, (fig. 6.) 



D. Cancellate. (fig. 7.) 



E. Tapering, (fig. 8.) 



Shell miivalve, spiral. Aperture coarctate, round, 

 entire. 



The shells of the genera Turbo and Trochus 

 are extremely similar, and are much intermixed in 

 the Linnaean arrangement ; yet the round aperture 

 of the one, and the angular form which characterizes 

 the other, ought sufficiently to point out to which 

 each belongs. The probability is, however, that 

 the Turbines which have escaped from their pro- 

 per genus, are fewer than the strangers which have 

 been admitted into it. The rotundity of the 

 mouth is a less indeterminate diagnosis than that 

 of almost any other genus ; and even in these spe- 



