340 VENERID^E. 



SHELL nearly globose, with a squarish outline in young and 

 half- grown specimens (which are not so convex as the adult), 

 very thick and opaque, of a dull aspect: sculpture, strong, 

 laminar, and pretty equally distant concentric ridges, which 

 are imbricated or fold backwards, and become more or less 

 warty or tubercular, especially towards the front margin and 

 sides, besides much smaller intermediate lamina? ; these pro- 

 cesses as well as the furrows are crossed by numerous but 

 slight and sunken riblets, which radiate from the beaks, and 

 by intersecting the ridges give the shell in its younger state 

 a cancellated appearance, and in its full-grown state the warty 

 or tubercular appearance above described ; the entire surface 

 is also covered with the microscopical stria3 noticed in other 

 species : colour yellowish-brown, with occasionally three or 

 four reddish-brown or purplish rays, which are sometimes 

 broken or zigzag : epidermis fibrous, brown, only to be seen 

 on the edges of the valves : margins similar to those in the 

 last species : beaks small, not prominent, recurved, and slightly 

 separated: lunule rather heart-shaped than lanceolate, reddish- 

 brown, denned by a distinct groove, closely imbricated length- 

 wise ; lips prominent and flexuous : corselet rather wide, finely 

 imbricated obliquely by a section of the inner lines of growth : 

 ligament narrow, homcolour, exposed : hinge-line obtusely 

 angular : hinge-plate thick, broad, and flexuous : teeth, in the 

 right valve three divergent cardinals, of which that in the 

 middle is the strongest and double, the anterior is pointed, and 

 the posterior is slighter and longer than the others, and nearly 

 parallel with the hinge -line ; the left valve has also three 

 similar cardinals, the anterior being the smallest, the middle 

 one very thick and slightly cloven, and the posterior resembles 

 the corresponding tooth in the opposite valve, but is stronger ; 

 laterals obscure : inside chalky- white, with a purple stain on 

 the posterior side ; margin notched in front and on the anterior 

 side : scars as in the last two species. L. 1-8. B. 2. 



HABITAT: Sandy gravel, in 7-20 fathoms, on the 

 south and west coasts of England, in the Channel 

 Isles, Milford Haven, Fishguard, and Pwllheli in North 

 Wales ; Oban ( J. G. J.) ; Tyree (Bedford) . Laskey says 

 that a specimen was dredged "at Dunbar, of an un- 

 common size," and it has been found by Macgillivray 

 at Aberdeen, and by others on several parts of the coast 



