XXIV HISTORICAL SKETCH. 



based upon it are almost always artificial. Still, the attempt to use 

 internal features was in itself a move in the right direction. 



The above classification paved the way for the great work of Dr. 

 Carl Semper, Reisen im Archipel der Philippine!!, Landinollusken. 

 In this, the most extensive work yet published upon the soft anato- 

 my of land mollusks, a great number of genera in all families of 

 snails are made known anatomically, the following scheme of classi- 

 fication being adopted. 



Family ZONITID^E : tail with gland ; marg. teeth aculeate, etc. 

 Family HELICID^E : no caudal mucus-gland. 



Vitrininse: Sole divided, margined; jaw smooth; marginal teeth 

 thorn-like. Limax, Vitrina, Parmacella, Vitrinoconus, 

 Vitrinoidea, Hyalina. 

 Helicinse : Sole undivided ; jaw various; marginal teeth short, 



several-cusped. 

 Oxygnatha : 



Teeth unicuspid : Acavus, Gorilla, Caryodes, Panda, Cara- 



colus, Labyrinthus. 

 Teeth broad, several-cusped. 

 Tentacles 2 . Janella. 



Tentacles 4; jaw with accessory plate: Succiuea. 

 Tentacles 4 ; jaw with no accessory plate: Oopelta, 

 Trochomorpha, Planispira, Obbina, Strophia, 

 Sagda. 

 Aulacognatha : Philomycus, Cionella, Tornatellina, Stenogyra, 



Endodonta, Buliminus, Pupa. 

 Odontognatha : 



No accessory organs on genitalia: Achatina, Amphidro- 

 mus, Bulimus, Otostomus, Partula, Hadra, 

 Pleurodonta, Polygyra, Trachia. 



Genitalia with accessory organs: Cochlostyla, Chloraa, 

 Eulota, Xerophila, and other genera [this group 

 of Semper's is the foundation of v. Ihering's 

 " Helicidse " and Pilsbry's " Belogona "]. 

 Goniognatha : Orthalicus. 

 Agnatha : Rhytida, etc., etc. 



Family ONCHIDIDJE. 

 Family VAGINULIDJE. 



Although founded upon the arrangement of Morch, this classifica- 

 tion exhibits a distinct advance, not only in the recognition of the 



