DESCRIPTION OF A NEW SPECIES OF 

 ACROPTYCHIA. 



By EDGAR A. SMITH, F.Z.S., 



Zoological Department, British Museum. 



Only two species of this genus have as yet been described, both 

 from Madagascar, and the species under consideration was also 

 obtained at the same island. A. metableta* of Crosse and Fischer, 

 the type of the genus, is one of the most remarkable operculated 

 land-shells on account of the lamellae (former peristomes) which 

 ornament the last half of the body-whorl. The second species, 

 A. cequivoca, Pfeiffert (syn. A. manicata, Crosse and Fischer \) has 

 quite the form of the type, but only a single lamella just behind the 

 aperture. Considering the similarity in shape, sculpture, epidermis, 

 operculum, and colour, it should perhaps be regarded as a variety 

 rather than as a distinct species. On the contrary, M. Mabillett 

 appears to have discovered sufficient difference to separate it not 

 only specifically, but even generically ! But this may have arisen 

 from the possible fact that he either did not know Acrqptychia, or it 

 did not occur to him to compare his so-called new genus Anceyiella 

 with it. At all events, he does not mention either of the species 

 described by Crosse and Fischer, and evidently was not aware that 

 A. cequivoca, the type of his genus Anceyiella, was identical with 

 Acroptychia manicata. 



On the other hand, if M. Mabille knew the genus Acroptychia at 

 the time, it shows what very feeble characters are estimated of 

 generic importance by a certain class of conchologists. If the 

 presence of one lamella, instead of several, is sufficient to distinguish 

 a species generically, why not separate a Mitra with three folds on 

 the columella from those with four or more, a Triton with several 

 varices from another with few, a Sea/aria with distant varices from 

 those in which they are very numerous and close-set ? To form 

 genera on such very slight differences in sculpture is simply 



* Journ. de Conch. (1874), 76 pi., pi. 1, f. 5-5!), also in Grandidier's Hist. Phys. Nat. et pol. 

 de Madagascar, Vol. xxv. , Mollusques, pi. 24a, f. i-4a. 



t Reeve's Con. Icon Cyclostoma, fig. 40. 



t Journ. de Conch. (1882), p. 325 ; Grandidier's Madagascar, pi. 24a, f. 5-5C. 



ft Bull. Soc. Philomat. (1885), Vol. ix., p. 128. 



