GASTEROPODA. 



163 



This genus embraces the species (Bulla) aplustre, physis, 

 and velum ; the latter is a very delicate shell, of a very 

 light horn colour, with a snow-white band about the 

 middle, bordered on each side by one of a dark brown 

 colour; the apex and base are white, both bordered by 

 dark brown bands. 



Cylichna. Loven. (Bullina Bisso.) — Shell cylindri- 

 cal ; spire either very small or none, and the apex um- 

 bilicated; columella thickened, with or without a plait; 

 shell either strong, smooth, striated, or grooved ; no oper- 

 culum. Animal not investing the shell; its head de- 

 pressed, subquadrate, truncate in front, produced pos- 

 teriorly into two, more or less separated, broad tentacula, 

 in front of whose bases are the more or less distinct eyes ; 

 lateral lobes reflected more or less distinctly on the shell ; 

 mantle with a posterior process or lobe ; foot oblong, 

 shorter than the shell ; tongue with a single row of sub- 

 quadrate axile teeth, with inflexed serrulated apices : these 

 are flanked on each side by several uncinated laterals, the 

 innermost ones much larger than the others ; no gizzard.* 

 — Several species ; also fossil. 



There are seven British species, the pretty C. cylin- 

 dracea of Pennant being one of them. Bulla truncata 

 Ad. ; umbilicata Mont. ; and acuminata Brug. ; belong to 

 this genus. 



Amphisphyra. Loven. (Utriculus Brown.) — Shell 

 thin, inflated, ovate or sub-globose ; whorls of the spire 

 exposed, depressed, with a mamillated nucleus ; aperture 

 expanded, not extending above the body whorl, outer lip 

 sinuous, produced, inferiorly retiring at its junction above ; 

 pillar lip sub-umbilicated ; no operculum. Animal, capable 



* Forbes' British Moll. 



