162 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 HelicincK, 

 nearly all' those of the Achatince 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 Helicince, or testaceous snails, having 

 perfect turbinated shells more or less depressed ; the 

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

 or spiral snails, the spire of whose shells is elongated 

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

 only two depressed or flattened tentacula, and no oper- 

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

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

 5. the LucernincB, 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^J. 



Sub-families Families Families 



of Analogical Characters. of the of the 



HelicidcE. Phytophaga. Zoopkaga. 



ACHATIN/E. Spire mostly produced. TROCHID.E. MURICID^E. 



LIMNACIN.E. Outer lip considerably dilated. TURBIDJS. STROMBIM:. 

 Animal much larger than its' 



loped in its mantle. 

 {Depressed, or the spire very} 



LUCERNINJE. 4 small; aperture furnished >HALJOTID^. 

 c with plaits. J 



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 Feru?sac to substitute a 

 new and artificial nomenclature of his own for the Hcttcidte, 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. 



