CHAP. VII. GENERA OF THE TURBIN.E. 20? 



here chiefly confine our notices to the five leading genera : 

 these appear to be Scalaria Lam., Turritella Lam., Turbo 

 Humph., Melampus Mont., and Scissurella D'Orbigny. 

 (190.) The genus Scalaria, as the circular-mouthed 

 group, represents Cyclostoma : the typical form seen in 

 the common wentletrap (S. pretiosa Lam.) has no pillar, 

 although it is a long spiral shell. These lead obviously to 

 Turritella, where the shell iseven more attenuated, so that 

 the whorls are fully as numerous as in Terehra, which it thus 

 represents. Turbo (pulchra,fg. 39.) is the next genus, 

 differing chiefly, as regards the sliell, 

 in the inner lip being broad and flat- 

 tened, and the spire often very short, 

 or not longer than the aperture. 

 There is certainly a resemblance be- 

 tween many of these shells and the 

 more globose Trochidce, particularly 

 the sub-genera Pagodella and Echi- 

 nella, which are not perlaceous ; but 

 the great thickness and depression 

 of the pillar in Turbo, its perfectly round aperture, and 

 the convexity of the body-whorl, are sure marks of dis- 

 tinction. In the invaluable plates of ]\L Quoy, there is 

 a figure of the animal of a species of Turbo (under the 

 name of Littorina), which shows it to have almost a 

 zoophagous structure, — so totally different indeed from 

 that of Trochu--i, that they have even no analogy to each 

 other. The same may be said of Phasianella, which is 

 only a long-spired Trochus, analogous, indeed, to Tu?-- 

 ritella, but with the short mouth and lateral filaments of 

 the TrochidcE. 



(191.) The next genus, Melnmpus Montf., is one of 

 particular interest. It was originally proposed by Lamarck; 

 but upon being told that they were land shells, he aban- 

 doned his name ofCono^ntlus, and incorporated the species 

 in his genus Auricula. This was clearly a retrograde 

 movement ; for, even had his information been correct, the 

 difference of these two genera on one hand, and the close 

 resemblance between Tornatella Sind Melampus, \k too ob- 



