242 Dr. PfeifFer's Observations on the Family Helicidae. 



7. Cylindrella e%«ws\Clausilia,Z.P/ei^er inWiegmann's 



8. crispulaj Archiv, Part I. 1839, p. 353. 



9. } torticollis (Claus. torticollis, Lam, 1.) 



The first five of these species are figured by Ferussac on the 

 163rd plate, and are referred by him to the subgenus Cochlo- 

 dina. Rossmassler calls them, (^Iconographie', Part II. p. 13.) 

 " long-necked Pupm" under which Sowerby {^ Genera of 

 Shells,') also classes some species belonging here. Whether 

 Clausilia torticollis, Lam. from Candia, must likewise be re- 

 ferred to Clausilia I will not venture to determine, as I am not 

 acquainted with the species, nor is the figure at present at my 

 disposal, and the description is slight, especially with reference 

 to the aperture. Yet much speaks in favour of this being its 

 true position. 



From what has been above stated it appears to me advan- 

 tageous to divide the family of the Helicidce into the following 

 genera : — 



1. Vitrina. 



2. Helicophanta. 



3. Succinea. 



4. Helios (with Carocolla and Anostoma, Lam.) 



5. Bulimus (with Achatina, Lam., Pupa, Drap., Partula, 

 Fer., and Megaspira, Lea.) 



6. Vertigo. 



7. Cylindrella. 



8. Clausilium. 



9. Polyphemus, Mont. 



The character which all have in common with the lAmacidee, 

 and by which they are distinguished from the following orders, 

 are the retractile tentacles provided at the apex with eyes ; and 

 the separate genera appear to me only in this way capable of 

 being sufficiently established according to correct principles. 

 Perhaps, however, some changes must be made in accordance 

 with the structure of the animals, as I am chiefly led to sup- 

 pose from some observations made on living specimens of 

 Bulimus hamastomu^. 



