288 HELICID.E. 



Crustacea. In 1819 the eldei: Baron Ferussac, in his 

 great work (or rather Prodromus to a work) on the Land 

 and Freshwater Mollusca, which was continued^ edited, 

 and published after his death by his son^ adopted the 

 genus Polyphemus of Montfort, in the synoptical table 

 which preceded this part of his work, for the species 

 comprised in the present genus, but added other species 

 which have no relation to those now under consideration. 

 Ferussac, however, in a subsequent part of the same 

 work, modified this view, and proposed to include this 

 miscellaneous assortment of species in a tenth subgenus 

 of Helix, which he called Cochlicopa. Tliis subgenus 

 he divided into two groups, one to contain the species 

 of Polyphemus, and the other [Stylo'ides) to contain 

 certain species of Achatina, as well as the Helix lubrica 

 of Miiller. In 1826 Risso republished Cochlicopa as a 

 separate genus, and restricted it to the above-named 

 species of Miiller; but the generic characters given by 

 him are very insufficient and in many respects incorrect. 

 In 1830 I proposed the genus Cionella, not being at that 

 time aware of Risso's publication ; and in my " Synopsis 

 of the Pulmonobranchous Mollusca of Great Britain,'' 

 which appeared in the ' Transactions of the Linnean 

 Society' (vol. xvi. p. 347), I gave the following descrip- 

 tion of this genus : — 



" Animal glutinosum. Tentacida inferiora brevissima. 



*' Testa oblonga, seu elongata ; anfractu ultimo majore. 

 Apex acutinsculus. Columella subinterrupta. Apertura cana- 

 liculata, ad basin subefFusa, marginibus ina^quahssimis. U771- 

 hilicus nullus." 



I also remarked that in this genus the columella forms 

 a sinus or channel in the aperture, though it does not 

 appear to be accompanied by any corresponding pecu- 

 liarity in the animal. The species which I referred to it 



