LUCINA. 241 



on the anterior side, which joins the ventral margin at almost a 

 right angle, rounded in front, somewhat truncate on the poste- 

 rior side, and sometimes indented by a slight furrow running 

 nearly parallel with the margin to the ligamental area, which 

 is very gently curved : beaks small and pointed, not project- 

 ing, slightly recurved, placed so close together as to touch, and 

 considerably nearer to the anterior side : lunule deep, abruptly 

 denned by the edges of the anterior margin : corselet, or liga- 

 mental area, also deep and well denned : ligament very long 

 and straight, horncolour, sunk within the dorsal margin, but 

 visible outside, with the exception of a small portion on the 

 sides, which is overlapped by a thin layer of shell : hinge-live 

 representing an obtuse angle, and occupying much more than 

 one-third of the circumference : hinge-plate rather broad and 

 strong : teeth, in the right valve one triangular and pointed 

 cardinal, and on each side of it a ridge-like lateral which is 

 raised at the end ; in the left valve two cardinals, one of which 

 is much smaller than the other, the laterals being less distinct 

 than in the other valve : inside nacreous and partly iridescent, 

 salmoncoloured in the centre ; margin bevelled off and plain : 

 scars large and distinct. L. 0-85. B. 1. 



Yar. minor. Shell smaller and flatter, with stronger and 

 more regular ridges. 



Habitat : A muddy and gravelly bottom, from 8 to 

 90 fathoms, on nearly all our coasts, but locally distri- 

 buted. It is much more common in the west of Scot- 

 land and Ireland than it is on the southern coasts of 

 England. Captain Beechey dredged it in 145 fathoms 

 off the Mull of Galloway. The variety occurs in deep 

 water off Shetland ; and there is a remarkable coinci- 

 dence in size between it and the southern specimens. 

 The geographical range of L. spinifera extends from 

 Nordland to the iEgean and Canary Isles. It occurs in 

 the upper miocene tertiaries of the South of France. 



Scotch and Irish specimens are far larger than those 

 from the south of England and the Mediterranean. 

 Young shells are exquisite objects, with their snow- 

 white complexion, occasionally suffused with a pale 



M 



