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 stria?, 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. ellipjtica, 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 iEgean, and the 

 Canary Isles. Nor is its bathymetrical 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' 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 iEgean as 15-140 fathoms. 



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

 alimentarv 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 



