14 CURRENT LITERATURE. 



NOTE ON THE AFFINITIES OF THE GENERA 

 LIMAX, ARION, AND HELIX. 



By R. F. Scharff, Ph.D., B.Sc, M.R.I.A. 

 Natural History Museum, Dublin. 



Hitherto it has been the practice among most conchologists to 

 place far too much reliance upon the nature of the lingual ribbon 

 in separating not only families and genera from one another, but 

 also species. The genus Arion has, for instance, been kept 

 persistently joined with Helix because their lingual ribbons 

 exhibit some resemblance to one another, whilst Limax has been 

 put into a distinct family for the opposite reason. And although 

 the fallacy of this view has been conclusively proved by Dr. Simroth 

 almost seven years ago, many conchologists are quite unaware of 

 this fact, and still look upon the radula as the most suitable and 

 reliable portion of the molluscan anatomy for the purposes of classi- 

 fication. The radula has certainly no claim to be looked upon as 

 constituting the anatomy of a mollusc, as some would have us 

 believe. If we examine Arion, Helix, and Limax anatomically, 

 we find that the two latter have a hard calcareous shell, whilst Arion 

 has none. Arion, on the other hand, has a caudal gland, but Helix 

 and Limax have no trace of such a structure. There is one 

 columellar muscle in Helix and Limax, whilst in Arion, instead of 

 it, there are three, viz., two widely-separated tentacular and one 

 pharynx retractor muscle. Two nerves run along the back to the 

 tail in Arion, whilst Helix and Limax agree in having only one. 

 At last, and this is the most important difference, in both Helix and 

 Limax the male portions of the reproductive organs are everted 

 during copulation, whilst in Arion the female portions fulfil that 

 function. 



CURRENT LITERATURE. 



Catalogue et Distribution Geographique des Mollusques Terrestres, 

 Fluviatiles et Marins d'une partie de I'lndo-Chine (Siam, Laos, 

 Cambodge, Cochinchine, Annam, Tonkin), par le Dr. Fischer. (PZxtract 

 from Vol. IV. of the Bull. Soc. Hist. Nat., Autun. iv\, 1891, 194 pp. 8vo). 



This is an extremely interesting and valuable catalogue of the mollusca of a 

 district, the conchological literature of which is too scattered to be within the 

 reach of many. During the last decade, the labours of L. Morlet, von 

 Mollendorff, Heude, Gredler, Crosse, and Fischer have immensely increased our 

 knowledge of the mollusca of China and Indo-China, as may be gathered from 

 the following list given by Dr. Fischer : 



