358 CYLICHNID^. 



fold in the inner lip, which is in the middle, flattened and pro- 

 jecting in the space of the aperture, being separated from the 

 fold by a deep insinuation ; the outer lip is generally somewhat 

 produced anteriorly, the aiiterior canal being distinct. Cre- 

 taceous, a. decurtata^ Sowb. 



? STOMATODON, Scely, 1861. Described from a cast in the Cam- 

 bridge Greensand. May be a Ringicula. R. polita^ Seely. 



CiNULiA, Gray. 



Distr. — 25 sp. Cretaceous ; Europe, United States. G. 

 globulosa, Desh. (Ixxxviii, 58). 



Shell globose, spire short, surface spirally sulcated, aperture 

 anteriorly produced, effuse, columella terminating with a single 

 oblique and twisted fold. 



OLiGOPTYCHA, Meek. Shell with spire much depressed and 

 obtuse ; outer lip smooth within, and very slightly sinuous at 

 the base of the aperture ; inner lip bearing a single, very promi- 

 nent, nearly transverse plication or tooth at the base of the 

 columella. Actseon concinnus, Hall and Meek (Ixxxviii, 59). 



AVELLANA, d'Orb. Shell globose, inner lip with two or three 

 folds, one being anterior, often bipartite, placed at the termina- 

 tion of the columella, the other subanterior, separated from the 

 former by a deep insinuation of the lip ; there is generally a 

 third one placed about the middle of the inner lip, and one or 

 two posterior, much shorter ones, but these are not constant. 

 A. inc7-afisaia, d'Orb. (Ixxxviii, 60). 



Family CYLICHNIDJE. 



Shell external, spiral, more or less cylindrical, usuallj- white. 

 No operculum. Animal with depressed quadrangular head ; 

 truncated in front ; bilobed behind ; with eyes at the base of 

 tentaculiform lobes ; foot rather narrow, truncated in front. 

 Teeth, central none, laterals 6"6, the inner large and hooked, the 

 outer small and uniform, rarely wanting. 



Cylichna, Loven. 



Syn — Bullina, Risso. 



Distr. — 40 sp. Chiefly deep-water shells. United States, 

 Greenland, Britain, Red Sea, Australia. Fossil. Triassic — . 

 C. a.rachis, Quoy (Ixxxvii, 30). 



Shell strong, cylindrical, smooth or punctate-striate ; spire 

 minute or truncated ; aperture narrow, rounded in front ; colu- 

 mella callous, with one plait. 



MNESTIA, H. and A. Adams. Shell oval, subcylindrical, banded, 

 with revolving striae ; aperture narrow, prolonged into a point 

 at both ends. C. 'niarmorata^ A. Ad. (Ixxxvii, 31). 



CYLicHNELLA, Gabb. Shell subcylindrical, spire sunken ; mouth 



