BOTHRIOPUPA. 233 



tubular, though generally very slender, sometimes umbilicate, 

 but usually closed at the base. In forms which have not de- 

 generated in the teeth there is usually a subcolumellar lamella 

 as well as a columellar. Many species have a tendency to 

 form accessory folds on the peristome or in the throat. 



The variety of shape, size and aperture is so great that a 

 diagnosis of the supergeneric group is hardly practicable 

 from the shells alone, and as yet we have not enough knowl- 

 edge of the soft anatomy to be of use in this connection ; yet 

 the aberrant forms, which make a group diagnosis impossible, 

 are united with the typical members by chains of species in- 

 termediate in character. 



As fossils, very few forms which seem quite closely related 

 to recent species of Abida have been found in the Oligocene, 

 possibly the Eocene, of England, northern France and Ger- 

 many, followed by a few Miocene species of Germany and 

 Bohemia. See under Abida. It may be inferred that the 

 group is a very ancient one, but its original habitat is prob- 

 lematic. 



The following genera are included : 



a 1 . South African. Fauxulus, p. 234. 



a 2 . Palaearctic (Europe, northern Africa, western Asia). 



b 1 . Shell conic or globosely conic, umbilicate or closed, 



with a rather large columellar axis; aperture fully 



toothed in the typical positions, the plicae short and 



marginal. Odontocyclas, p. 254. 



b 2 . Shell cylindric, turrite or fusiform. 



c 1 . Umbilicate, the internal axis large. SandaMia. 

 c 2 . Internal axis slender. 



d 1 . Fully toothed ; palatal plicae, or part of 



them, very long; radula with teeth of 



normal Pupillid type. Abida. 



d 2 . Palatal plicae of moderate length, short 



or wanting. 



e 1 . Shell small (3 to 5 mm. long, 4%-6 

 whorls), rather slender, thin, pale 

 or dull brown; teeth of radula of 



