94 BRITISH MOLLUSKS. 



closely convoluted into a rather narrow, subcylindrical, oblong form, 

 transparent in substance, and with, a shining, glossy surface. The 

 aperture is small, and the lip is peculiarly callous, the base of the 

 right margin being marked by a subtruncate, faintly angular in- 

 dentation. The species is more generally known to collectors by its 

 name of lubrica, but modern writers have restored to it the Linnean 

 name subcylindrica. Doubts have been entertained of this being 

 the Linnean Helix subcylindrica, because that species is described 

 in the ' Systema Naturae ' as inhabiting water. The animal can, 

 however, exist some time under water, and is not unfrequently found 

 amid the floods and overflows of rivers. 



Azeca tridens. (Enlarged.) 



Genus VII. AZECA, Leach. 



Animal ; body oblong, attenuately rounded in front, converging to 

 a point behind, dingy speckled grey, moderately tubercled, 

 carrying a cylindrical chrysalis-shaped shell, upper pair of ten- 

 tacles slender where exserted. 

 Shell ; cylindrical, attenuately contracted at the base, shining 

 horny, smooth, whorls seven, convex ; aperture small, con- 

 tractedly ear-shaped, toothed within, lip forming an opake 

 continuous rim. 

 Azeca is by no means, as some have ventured to assert, the same 

 generic form as Zua, with no other difference than a toothed aper- 

 ture to its shell. It is a mollusk of different distribution and habit, 

 and the shell has a totally distinct typical structure. On reaching 

 maturity, instead of being expanded, it is attenuately contracted, 

 and the aperture has a compressly distorted ear-like form. The 

 interior is furnished with three prominent teeth within, and some- 

 times with one or two smaller teeth. 



We have only one species of Azeca in Britain. It occurs but 

 sparingly in England, and has not been collected in Scotland or 



