XV111 HISTORICAL SKETCH. 



to classify the Helices into subgeueric 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 : 



f Redundantes. 



Volutatse, Helicoides, subgenus Helicophanta [ Daudebardia, 



Aerope, Helicophanta]. 

 Evolutse, Cochloides, subgenus Cochlohydra [=Succinea]. 



ff 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]. 

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



pe rforate, with entire mouth], 

 subgenus Cochlitoma [=Liguus, Achatina]. 

 subgenus Cochlicopa [ Glandina, Stenogyra, 



Ferussacia]. 

 subgenus Cochlicella, [=Cochlicella, Rumina, 



etc.], 

 subgenus Coc/i/o^e?ia[=Limicolaria, Bulimus, 



Achatinella, etc.]. 



subgenus Cochlodonta [=Pupa, Strophia, Gib- 

 bus, etc.], 

 subgenus Cochlodina [ Cylindrella, Clausilia, 



Buliaiinus], 



Each of these subgenera is divided into several groups designated 

 by terms expressive of their peculiarities, thus : 



( Lomastomse, ( Aplostomse. 



T^-,. ,, \ Aplostomaa, TT T * i \ Lamellatse. 

 b.-g. Helicella j H ^ romao ; s> S.-g. HehcostylaJ, CanaliculatJB . 



^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 



