204 Shell Life 



The Thick Top-shell {T. lineatus) is not pyramidal 

 but conical, very thick and dull. Young specimens 

 exhibit the spiral ridges, but these have disappeared 

 in the adult. The ground colour is yellowish or 

 greyish, overlaid by zigzag purple streaks. The 

 apex of the rather low spire is alwaj's eroded by 

 the time the shell is full-grown. Whorls 6 ; mouth 

 large and oval, the inner lips bearing a strong tooth- 

 like tubercle. Tlie large shallow umbilicus is partly 

 covered by the inner lip. Its measurements are an 

 inch either way. It is a local shell, but may be 

 found from Dorset to Cornwall, and up the western 

 coast to Anglesey ; also in Ireland and the Channel 

 Islands, between tide-marks. 



The Round Top-shell (T. diLininyi) is a minute 

 shell, which is equally convex above and below, 

 flat spired, and has a very wide and open umbilicus. 

 It is white, semi-transparent, glossy, and has fine 

 whorls spirally ridged. The mouth is almost square. 

 It occurs at Bundoran, Donegal Bay. 



The Flat Top-shell {T. iinnhilicatus) is much larger 

 (half an inch across) than the last, flat-based and 

 almost flat-topped, without any approach to the 

 pyramidal form. The spiral ridges are sharper and 

 fewer; the colour grey, streaked with red lines or 

 zigzags ; outer lip bordered with orange and green. 

 It occurs in numbers, feeding on the Saw-edged 

 Wrack (Facus serratus), in the littoral zone along 

 the south coasts up the Bristol Channel, around 

 Ireland and the Isle of Man, and along the west 

 coast of Scotland. 



The Grey Top-shell (T. cinerarius) is the most 

 abundant of all our Top-shells. It varies a good 



