10 NATICJD.E. 



some conchologists ; I have placed it in Tornatellidiu (See Struct, 

 and Syst. Conch., ii, 357). 



Genus RUMELLA, Bourguignat, 1885. 



Shell small, obliquely oval, polished, spire short, of few whorls ; 

 last whorl with a large umbilical depression, limited by a basal 

 angle, and covered by a strong rounded callus ; lip simple. Opcr- 

 culum unknown. 



Lake Tanganika, Central Africa. 



The species are said to resemble the group Mamilla in minia- 

 ture; their position cannot be positively ascertained until we 

 become acquainted with the animal and operculum. 



Genus SIGARETUS, Lamarck, 1799. 



Shell depressed ear-shaped, with minute spire and very large 

 aperture, externally with revolving striae; color usually white, 

 sometimes invested with a thin corneous epidermis. Operculum 

 minute, horny, paucispiral (PI. 1, fig. 15). 



Animal with large mantle partly or entirely covering the shell 

 into which it is not able to withdraw entirely. Dentition. 

 Central tooth of the radula shorter than the lateral cusps (PI. 1, 



;-' ") 



Sigaretus inhabits warm seas, on muddy sand-flats ; it is slug- 

 gish and very timid, moving slowly; when crawling they con- 

 stantly explore the surrounding surface with the produced fore- 

 lobe of the foot, which is also used in burrowing. 



Living species are rather numerous; fossil, it commences in 

 the Cretaceous. Catinu* (Klein, 1753), H. and A. Adams; 

 Lnpia, Conrad ; Stomatia, Hill ; Cryptostoma, Blainv., 1818, and 

 Raynevallia, Ponzi, are synonyms. 



Section SIGARETUS (.se/zsw. stricto). 



Shell depressed orbicular, convex above, mouth rounded ; 

 umbilicus none or covered by a reflection of the inner lip ; spire 

 short, oblique. 



Section EUNATICINA, Fischer. 1885. 



Shell umbilicated, oval oblong, thin, ventricose ; spire sharp; 

 inner lip straight, thin anteriorly, with a median callus. N. 

 papilla, Gmel. 



It is Naticina, Gray, 1840 (not Guilding, 1834). Lacunaria, 



