Mr. J. Miei's on the genus Scopolia. 35 



an incomplete umbilicus that is very conspicuous in some spe- 

 cies, in others almost closed up, and often in the same species, the 

 Puteoli, it is sometimes apparent, and frequently scarcely visible ; 

 in all other respects these Lacunce are similar to the LittorincB. 

 In opposition to these pretensions, I repeat, that all the so-called 

 LacundB have invariably the form of the pedal disc of the Litto- 

 rincB, accompanied by the overwhelming characteristic vermicular 

 alternate quality of progression which is almost exclusively con- 

 fined to that genus, and which must, as I think, fix the Lacuna 

 of authors for ever as one of its sections. 



With regard to the aid derived from the tongues of the Gas- 

 teropoda for generic or specific distinction, I am inclined to think 

 its importance overrated, because no two species of the same 

 genus have a precisely similar disposition of the rachis, uncini, 

 and arrangement of the spines and interweavings of the lingual 

 riband : this fact sets at rest generic views ; the tongues, at best, 

 are of mere specific value : I have examined hundreds, and can 

 make nothing of them that can at all be depended on, from their 

 extreme variable structures. The tongues of great numbers of 

 the minor species cannot without extreme difficulty be obtained 

 by the scalpel, they can only be detected after maceration and 

 compression under a powerful microscope, and the comparison of 

 these minute species is attended with difficulties and very unsa- 

 tisfactory results. The ootheca of the mollusca may be useful in 

 comparison, if they can be obtained and identified to belong to 

 certain species. 



I conclude, and insist on the foregoing positions in the paper 

 and postscript, with as much tenacity as courtesy will allow to the 

 phrase ; I cannot even consent that the Lacunce be considered a 

 subgenus of the Littorince ; I think the term subgenus an unsa- 

 tisfactory and hybrid expedient, to attempt to express an inter- 

 mediate state that does not exist ; with me subgenera are resolved 

 either into distinct species or genera. If I might consider that 

 those who use the term subgenus mean to define it as an aggre- 

 gation of particular or aberrant species of a distinct genus, I would 

 accept the definition, but not the term, which ought to be sec- 

 tion, as that of subgenus seems to imply something beyond divi- 

 sional arrangement. — W. C. 



V. — On Scopolia, Anisodus and Mandragora. 

 By John Miers, Esq., F.R.S., F.L.S. 



Scopolia. 



A SINGLE species only of this genus is recorded, and it seems 

 to possess a considerable range, for it is found in Illyria, Croatia, 



3* 



