LIJCINA. 243 



rior side, which is indented by an indistinct furrow running 

 nearly parallel with the ligamental area : beaks very small and 

 pointed, rather prominent, much recurved, almost contiguous, 

 considerably nearer to the anterior side : lunule deep and ex- 

 cavated : corselet level : ligament very long and straight, yel- 

 lowish-brown, seniicylindrical, slightly projecting outside ; its 

 sides are covered by a shelly strip, which is usually found 

 broken in small pieces by the action of closing the valves : 

 hinge-line curved, occupying not quite one-third of the circum- 

 ference : hinge-plate broad and thick : teeth, in the right valve 

 two strong cardinals, the anterior one being double, and the 

 posterior much smaller and set more obliquely, and on each 

 side of the beak a plate-like lateral, the anterior one being 

 slightly raised at the end, and the posterior much longer than 

 the other ; in the left valve two similar cardinals, but nearly 

 of equal height, and corresponding laterals : inside chalky- 

 white, but in places irregularly tubercular from an internal 

 deposit of nacre : margins bevelled off and plain, sometimes 

 grooved longitudinally : sears remarkably large and distinct. 

 L. 1-4. B. 1-5. 



Yar. 1. depressa. Shell natter and thinner, with fewer ribs 

 and the beaks less prominent. 



Yar. 2. gibba. Shell much smaller, with a more oblique 

 outline, the valves protuberant, ribs closer together, epider- 

 mis iridescent, and the beaks more prominent. L. 0-45. 

 B.05. 



Habitat : On all our coasts, in muddy gravel and sand, 

 from the low- water mark of spring tides to 82 fathoms. 

 Captain Beechey has dredged it off the Mull of Gallo- 

 way in 110-145 fathoms. The late Wm. Thompson and 

 II . Ball found it in lakes of brackish water at Arran. 

 Dr. Lukis informed me that this species was compara- 

 tively rare in the Channel Isles, and that the numerical 

 proportion which it bore there to Loripes lacteus was as 

 1 to 50. He added, " Lucina borealis was wrongly stated 

 by Forbes and Hanley (vol. ii. p. 48) to occur ' abun- 

 dantly near St. Peter's Port in Guernsey/ We do not 

 meet with it excepting at Herm. I have never found a 

 single specimen on the Guernsey coast, although I have 



m 2 



