334 SMITH : NOMENCLATURE OF CERTAIN GENERA. 



to annul it. Such being the case I think the name Viviparus 

 must be adopted, a view taken by Binney, Bourguignat, Uupuy, 

 Clessin, Kreglinger, Locard, Frauenfeld, H. and A. Adams, and 

 others. 



Some may not agree with the use of the same term for both 

 specific and generic names, considering Viviparus viviparus 

 objectionable. But this double employment of names is admitted 

 by many persons in other branches of zoology :^for instance 

 Lutra lutra for the otter ; Merula nierula for the blackbird ; 

 Pica pica for the magpie ; Bufo bufo for the toad ; Scomber 

 scomber for the mackerel ; Thynnus thynnus for the Tunney, &c. 



It may also be urged that generic names derived from 

 adjectives, like Viviparus, are not admissible. True, it is not 

 advisable to employ such terms in future, but, if it were decided 

 that such names must be cast aside, we should have to part with 

 the old familiar genera Vitrina, Productus, Achaiina, Succinea, 

 lanthina, and many others. 



My own opinion is to let remain names such as these which 

 were proposed before the laws of nomenclature were so well 

 known and respected as at present. 



AMPHIPEPLEA. 



This is one of those divisions which I think may fairly take 

 generic rank. It is acknowledged of such importance in the 

 Manuals of H. and A. Adams, Tryon, Philippi, and Fischer, 

 and almost without exception by recent Continental writers. 



Although the British species which comes in this group, 

 viz., A. glutinosa (Muller), appears in the works of Jeffreys, 

 Reeve, Forbes, and Hanley, and the Conchological Society's 

 list under Limncea, still, in each case, the propriety of its 

 separation is more or less hinted at and discussed. The points 

 in which it differs from the true LimncecE are (i) the greater 

 development of the mantle, which is capable of reflexion, so as 

 almost entirely to conceal the shell, which is very thin and 

 glossy, (2) certain peculiarities in the nervous system, having 



J,C., vi., Apr., 1891, 



