152 SHELLS AND SHELL-FISH. PART I. 



both the animals and the shells are more diversified. 

 Hence, while scarcely any thing has yet been done in 

 determining the genera and sub-genera of the Helicino', 

 nearly all those of the Achatints have been named and 

 defined. It is time, however, to quit these general 

 remarks, and proceed to the sub-divisions of the family. 

 (153.) We arrange the whole of this group under 

 the five following families, which may be thus de- 

 fined : — 1 . the HelicincB, or testaceous snails, having 

 perfect turbinated shells more or less depressed ; the 

 aperture entire, but without teeth. 2. The AchatincB, 

 or spiral snails, the spire of whose shells is elongated 

 and conic. 3. The Limnacince, or river-snails, having 

 only two depressed or flattened tentacula, and no oper- 

 culum. 4. the Limacince, or slugs, having either no 

 shell, or one much too small to contain the body. And 

 5. the Lucernincs, or terrestrial volutes, where the shell 

 is orbicular, depressed, or flattened, and the aperture 

 furnished with distinct teeth.* That the foregoing 

 series is probably the natural one, may be inferred from 

 the following table of analogies : — 



Analogies of the Helicid^. 



These analogies are, of course, only applicable to the 

 types of each, and are intended to be so understood : 



* The injustice of the attempt made by M. de Ferussac to substitute a 

 new and artificial nomenclature of his own for the Hclicidce, and so to 

 cancel the previous generic names of Lamarck, Draparnaud,and of all his 

 predecessors, is without parallel in this or perhaps any department of zoo- 

 logy, and can only be equalled by the confusion it has caused. 



