XV111 HISTORICAL SKETCH. 



to classify the Helices into subgeneric groups. After dividing the 

 shell-bearing terrestrial inoperculate pulmonates into six genera, 

 Helixarion, Helicolimax, Helix, Polyphemus, Vertigo and Partula, 

 Ferussac proposes the following system for Helix : 



t Redundantes. 



Volutatse, Helicoides, subgenus Helicophanta [ Daudebardia, 



Aerope, Helicophanta]. 

 Evolutse, Cochloides, subgenus Cochlohydra [=Succinea]. 



ft Inclusse. 



Volutatse, Helicoides, subgenus Helicogena [=all globose Helices], 

 subgenus Helicodonta [=all toothed Helices], 

 subgenus Helicigona [=all keeled toothless 



Helices], 

 subgenus Helicella [^depressed, mostly simple 



lipped Helices and Zonitidce]. 

 subgenus Helicostyla [=elevated Helices, not 



keeled]. 

 Evolutse, Cochloides, subgenus Cochlostyla [=Bulimoid forms, im- 



pcrforate, with entire mouth], 

 subgenus Cochlitoma [=Liguus, Achatina]. 

 subgenus Cochlicopa [=Glandina, Stenogyra, 



Ferussacia]. 

 subgenus Cochlicella f [=Cochlicella, Rumina, 



etc.], 

 subgenus Cochlogena [=Limicolaria, Bulimus, 



Achatinella, etc.]. 



subgenus Cochlodonta [Pupa, Strophia, Gib- 

 bus, etc.], 

 subgenus Cochlodina [=Cylindrella, Clausilia, 



Buliminus]. 



Each of these subgenera is divided into several groups designated 

 by terms expressive of their peculiarities, thus : 



!Lomastomse, f Aplostomse. 



Aplostomse, G rr 7 . . / I Lamellatse. 

 Hygroma De8 , ^ Helwostylal Canaliculata , 

 Heliomanes, [ Marginatse. 



These divisions of the subgenera were not intended in the sense of 

 sub-subgenera and should not be used in such sense. Many of them 



