56 LUCINIDiE. 



side is very considerably the smaller and the narrower one. 

 The umbones are rather prominent, and incline forwards ; 

 the beaks are small and acute ; in front of them is a rather 

 large not very profound subovate lunule. The ligament is 

 partially concealed by the overlapping margins. There is 

 a single erect obscure primary tooth in the right valve : the 

 anterior muscular impression is double. 



The average breadth of specimens is about three-eighths 

 of an inch, and the length is somewhat less. There is a 

 closely-allied Swedish shell, the Axinits Sarsii of Philippi 

 (Loven, Ind. Moll. Skandinav. \>. 38), which differs in being 

 larger, more orbicular, less angular in contour, almost 

 opaque, devoid of the cardinal denticle, having its lunule 

 almost obsolete, and the front angle perfectly so. 



The animal, judging from a specimen preserved by Goad- 

 by^ fluid, is of a white colour, and has a widely-gaping 

 mantle, with two orifices, but no appearance of prolonged 

 tubes posteriorly. The foot is very long, almost filiform, 

 cylindrical, tubular, and presents a clavate extremity. 



This beautiful shell is widely distributed around our 

 shores ; though, from its delicacy and fragility, and the 

 facility with which the valves separate, perfect specimens 

 are comparatively rare in our cabinets. Mud, or muddy 

 sand is its favourite bottom, and in some places it is found 

 on such ground in considerable numbers. Among its locali- 

 ties may be enumerated, — Weymouth, in seven fathoms, 

 and Dartmouth, in nine fathoms (M'Andrew and E. F.) ; 

 Exmouth (Clark); Torbay (Alder and S. H.); Falmouth, 

 and other parts of Cornwall (Jeffreys and Alder) ; Coast of 

 Glamorganshire (Jeffreys); Tenby, where single valves are 

 very abundant (S. H.); Anglesea (M'Andrew); Isle of 

 Man, twelve fathoms, but rare (E. F.); Scarborough 

 (Bean); Coast of Northumberland and Durham (Alder). 



