156 HELICID^. 



Shell hardly a quarter of an inch long, and a third 

 of its length broad, of a glossy brown or horn-colour, 

 with often a reddish tinge, quite smooth and polished; 

 spire composed of five or six raised volutions ; aper- 

 ture narrow-oval, with the margin thick and not 

 reflected, often of a rosy colour. 



Varies in shape, size, and colour, sometimes trans- 

 parent greenish white. 



This species was first figured as English by Lister 

 {Anim. Ang. t. 2. f. 7.) and Petiver {Gaz. t. 30. f. 7.) 



8. AzECA Leach. (Trident Shell.) 



Animal like Bulimus, with subcylindrical, rather 

 obtuse shell, covered with a polished periostra- 

 cum ; aperture pear-shaped, curved and pointed 

 at the top; the margin thick, obtuse, and united 

 all round and toothed ; the axis imperforated. 

 In shape, colour, polish, and habitat, this shell so 

 exactly resembles the Bi/lhnus luhriciis, that some 

 have questioned if this latter shell be not the same in 

 its earlier stage of formation before the teeth appear ; 

 but the singular shape of the aperture decidedly re- 

 moves it into a distinct genus, which is adopted from 

 Dr. Leach. The jaw is lunate, narrow, crenulated 

 on the edge. 



Mr. Alder considers this genus as intermediate 

 between Bulimus and Clausilia, resembling the former 

 in shape, and approaching more to the latter in having 

 the peristome complete, and also more particularly in 

 having a longitudinal plate on the columella, consi- 

 derably within the aperture, similar in situation and 

 making a slight approach in form to the clausium 



