LIMA. 83 



SHELL oblong, extremely convex, rather thin and glossy, 

 semitransparent : sculpture, 24 slight but sharp ribs, which 

 radiate from the beaks and do not extend to the sides ; the 

 middle rib is the largest, and runs straight down to the front 

 margin ; the ribs are crossed by extremely fine and numerous 

 concentric striae, making the crests appear somewhat jagged : 

 colour milk-white: margins rounded in front, and sloping with 

 a gentle curve upwards to the ears : beaks extremely promi- 

 nent and gibbous, projecting considerably beyond the hinge : 

 ears triangular, very small, hanging a little downwards : carti- 

 lage diamond-shaped, occupying nearly one-third of the hinge : 

 ligament narrow and slight : hinge-line straight except in the 

 middle, where it is incurved : hinge-plate sharp : cartilage-pit 

 forming an acute triangle, faintly striate across ; under each 

 ear is a shelving triangular space as in L. elliptica, but pro- 

 portionally narrower : inside highly nacreous, and marked by 

 a furrow which runs down the middle, and is the reverse or 

 under side of the central rib ; it is also indistinctly grooved 

 by the impression of the outside ribs ; front margin slightly 

 notched by the edges of those ribs: muscular scar faint. 

 L. 0-275. B. 0-15. 



HABITAT : Sandy and gravelly ground in almost every 

 part of the British seas, from 18 to 90 fathoms. It is 

 also a Coralline Crag fossil. Its distribution in other 

 parts of the northern hemisphere is very extensive, em- 

 bracing Greenland, Iceland, Scandinavia, the Adriatic, 

 both shores of the Mediterranean, the ^Egean, and the 

 Canary Isles. Nor is its bathy metrical range in widely 

 separated seas less worthy of remark. Wallich obtained 

 it by means of his deep-sea soundings in the North 

 Atlantic from 227 fathoms ; and M f Andrew has recorded 

 the depths at which he dredged living specimens on the 

 coast of upper Norway as 15-150 fathoms, and Forbes 

 in the ./Egean as 15-140 fathoms. 



The animal is shy. It uses its foot for crawling. The 

 alimentary and branchial current enters in at the middle 

 of the front margin ; and the excretory current passes 

 out below the ear on the posterior side. In a single 



