HELIX. SNAIL-SHELL. 45 



Shell flattish, a little convex on both sides, semitrans- 

 parent, with a wide and deep perforation on the underside, 

 strongly and irregularly wrinkled, and crossed in an oppo- 

 site direction with very fine and minute strise, giving it a 

 kind of shagreened roughness : spires six, the larger one 

 sloping down on each side so as to form a sharp ridge on 

 the margin, which runs spirally throughout the upper vo- 

 lutions and marks their separation by a fine line, the edges 

 of which appear slightly toothed or crenate by the wrin- 

 kles : color dark horny, with deeper blotches : aperture 

 transverse, nearly oval, narrowed to a kind of angle where 

 it meets the keel, a little dilated in the middle, and round- 

 ed beneath with a thin sharp white margin which is slightly 

 reflected, and. dilated and a little spreading towards the 

 perforation : diameter three quarters of an inch j height 

 about three eighths. 



Woods, clefts of rocks, and old walls, v. v. 



2. Helix subcai inata. Subcannated Snail-shell. 



Montagu, pi. 7. f. $ Walker, f. 22. 



Trochus rugosus. Brown, Wern. Soc. pi. 24. f. 5. 



Shell rather convex, semitransparent, white or pale 

 rust-color, sometimes glossy, but generally appearing as if 

 frosted : spires four, well denned and finely striate longi- 

 tudinally, with two fine circular raised lines round the base 

 of the body volution and one on the upper part, which last 

 continues round the middle of the second volution, and .i 

 obliterated in the line of junction towards the top : from the 

 lower ridge at the base commences a semicircular channel 

 which terminates in a large and deep perforation : aperture 

 roundish oval ; the outer-lip projecting atid tlvn; inner-lip 

 reflected, spreading into a sharp angle, and raised on the 

 body of the volution : diameter one tenth of an inch ; height 

 more than half as much. 



In fine sand, on the western coasts, Kent, and Dublin 

 bay. v. m. 



3. Helix planorbis. Bordered Snail-shell. 



Montagu, pi. 25. f. 1. 



Helix planata, Linn. Trans, viii. pi. 5. f. 14 Dorset Cat. 

 pl. 20. f. 18. 



Shell 



