AxiNtrs. 245 



Palissy's workmanship impose on a palaeontologist of any 

 experience. The shell of L. borealis has a considerable 

 tendency to vary in respect of the remoteness or proximity 

 of the striae. In some Guernsey specimens the ribs 

 nearly disappear towards the front. A specimen from 

 Exmouth has a minute pearl lodged between the pallial 

 impression and the inner margin. The young are ob- 

 liquely triangular, and marked with a few irregular 

 white streaks which radiate from the beaks. The fry are 

 almost globular, perfectly smooth, and glossy. Speci- 

 mens of an extraordinary size are got at Tenby. My son 

 picked up a single valve on the sands there, measuring 

 two inches in breadth and nearly as much in length. 



Petiver first noticed this species as British, and called 

 it the " thread-girdled white Cockle." Donovan recog- 

 nized it as the Venus borealis of Linne. It is also the 

 V. spuria of Gmelin (from the figures of Lister and 

 Chemnitz), Tellina radula of Montagu, and Venus cir- 

 cinnata of Brocchi. The type of Turton's Lucina alba 

 is composed of two odd and much-worn valves of 

 L. borealis. The L. lactea and L. leucoma of Macgilli- 

 vray also belong to the present species. 



Genus III. AXFNUS *, J. Sowerby. PL V. f. 6. 



BODY convex : mantle having the margin thickened, with- 

 out tubes : gills two on each side, an outer and inner pair : 

 foot nearly cylindrical and very slender. 



SHELL globular, with somewhat of a triangular outline, 

 smooth ; posterior side longitudinally furrowed, or angulated : 

 beaks much recurved : lunide short and sometimes indistinct : 

 ligament usually and to a certain extent external, placed in a 

 groove or excavation on the hinge-line, and outside the hinge- 

 plate : teeth altogether wanting. 



* Hatchet-shaped. 



