144 



tions, and have not perhaps set sufficient value on those difFerences, 

 which they had an opportunity of observing ; while Adams saw great 

 differences, but from the want of many specimens feared to give spe- 

 cific importance to them. 



I should not have adopted the independent course of disregarding 

 previous naming or descriptions, nor attempt to propose new species, 

 had I possessed a few specimens of each only. But having of almost 

 every species pleaty of perfect specimens, and having them so arranged 

 that I knovy the precise habitat of almost all, I feel there is abun- 

 dant justification for my proceeding. Sowerby's description of the 

 operculum of C. corrugatus is (doubtless from causes before alluded 

 to) so very meagre, that it is utterly impossible to say to what shell 

 he referred. Pfeiffer, Gray, and Adams have all been misled : for 

 every Jamaican Cyclotus has its operculum " extus lamina elevatd." 

 But it will be found that the description which I shall give of the 

 operculum of C. corrugatus, does not militate with, but only enlarges 

 upon Pfeiffer' s, which is " with whorls, the margin of which is dila- 

 ted into broad, spirai, raised, somewhat expauded lamina." While 

 the shells which Adams has distributed, (and atp. 143, Cont. Conch. 

 has described with a "?") as C. corrugatus, and which Gray has 

 marked " C. corrugatus var." in the British Museum, militate very 

 strongly with Pfeiffer's description, and also exactly agree with the 

 opercular type of C. jugosus, which type is so peculiar that it can 

 hardly be supposed that Sovrerby would not have especially noted it. 



Aided by what now appear marked differences in other parts of 

 the shells, my principai guide to the new species I am about to pro- 

 pose has been the Operculum. I am aware that some have to a cer- 

 tain degree discarded the operculum as a specific tęst : yet a careful 

 examination of my Jamaican Cyclotus, — the careful gathering toge- 

 ther, all from one extensive and rich field, — mll tend to the conviction 

 that such a repudiation is not correct. We find the forms of opercula 

 constant in all other subgenera and species of Cyclostomidce, with 

 equal certainty in shape and sculpture ; and by more than analogy 

 the opercula of the Jamaican Cyclotus, accompanied by differences 

 in other parts of the shell, are specific guides and of specific import- 

 ance. 



I propose for consideration that there are six distinct forms of 

 opercula in the Jamaican Cyclotus, 



FoRM § I. that of C. corrugatus, Sow. 



Sowerby, in Pro. Z. S., 1843, p. 30, describes the operculum of it 

 as " testaceo, extus lamina elevatd, co7ivolutd; intus corneo, polito," 

 testaceous with elevated convolute lamina outside (or on the upper 

 side), and horny and polished on the under side. 



Pfeiffer, in Cat. Phan. p. 13, describes it as " with whorls, the 

 margin of which is dilated into broad, spirai, raised, somewhat ex- 

 panded lamina." 



I should describe the typical form of the operculum of that vvhich 

 I adopt as C. corrugatus, "with lamina rising more or less, and 

 well separated from the plane of the operculum, bending outwards ; 



