274 calyptrjeidjE. 



Shell usually much depressed and spread out (higher and 

 more conical when attached to a pebble), thin, semitransparent, 

 glossy at the point, but else of a dull and scabrous aspect : 

 ssulpture, numerous and fine minute striae, which encircle the 

 surface in a spiral direction, and are usually raised, so as to 

 form irregular rows of short vaulted scales ; marks of growth 

 indistinctly spiral : colour white, with frequently a yellowish 

 tinge at the point : becifc small, nipple-shaped, nearly erect, 

 representing the apex of the spire in turbinated univalves : 

 suture slight : mouth greatly expanded : inside porcelain-white, 

 rarely of a yellowish colour, highly glossy ; margin extremely 

 thin : diaphragm or rudimentary pillar occupying nearly one- 

 half of the posterior side ; its outline is obliquely triangular, 

 with rounded sides and a spirally incurved nucleus ; it is con- 

 cave, marked with delicate and close-set flexuous lines parallel 

 with the base, and has its inner margin double and con- 

 sequently thickened. L, 0-75. B. 0-75. 



Habitat : Local but gregarious, in shelly and pebbly 

 ground, on many parts of the Devon and Cornish coasts, 

 and in the Channel Isles, from low-water mark to a 

 few fathoms' depth ; Weymouth (Thompson) ; Milford 

 Haven, 10-12 f. (M 'Andrew and Jordan); "Dublin 

 Bay 9i (Turton) ; " a solitary small specimen has been 

 found near Dunbar }> (Laskey) ; " in Caledoniae Borealis 

 mari profimdo " (Leach) . The last two localities, and 

 probably the Irish one also, are erroneous : such state- 

 ments have considerably retarded our knowledge of the 

 distribution of the British Mollusca. It has been re- 

 corded as fossil from the Norwich Crag (S. P. Wood- 

 ward) \ Bed and Coralline Crag (S. Wood) ; Antwerp 

 (Nyst) ; faluns of Touraine (Cailliaud) ; Bordeaux 

 (Grateloup) ; Subapennine tertiaries (Brocchi) ; South 

 Italy and Sicily (Philippi) . Recent : — Coasts of France, 

 Portugal, Spain, Italy, islands in the Mediterranean, 

 Crimea, Morea, North Africa, Madeira, and Canaries, 

 from the shore to 55 f. 



It would seem that this mollusk seldom, if ever, leaves 



