4. convex a, Wood. 



5. Conradi, CourtJi. 



6. Corbuloides, Desk. 



7. cuneolus, Reeve. 



8. distorta, Moid. 



9. fabula, Reeve. 



10. granulosa, Ad. andRv. 



154 



11. magnifica, Jonas. 



12. Myopsis, Jfcfo'W. 



13. Novo-Zelandica, Rv. 



14. oblonga, «W. 



15. phaseolina, Lam. 



16. plicata, DesJi. 



17. pubescens, _P«W. 



18. rudis, Reeve. 



19. siliqua, eW. 



20. similis, CourtJi. 



21. squamosa, Carp. 



22. villosiuscula, Macg. 



Figure. 



Thracta Conradi. PL 42. Fig. 230. Shell, with one valve dropped to 

 show the thickened hinge-fulcrum, and external portion of the liga- 

 ment. 



Genus 8. NECERA, Gray. 



Animal ; oblong ; mantle closed in front, except a plain-edged 



orifice for the passage of a lanceolate foot ; sip/ions short, 



united, unequal, the branchial largest, both bearing a few long 



filiform cirr/ti at their sides, extending beyond the orifices ; anal 



siphon with a very extensile membranous valve. fForbes.J 



Shell ; oblong-pyriform, more or less beaked and gaping poste- 

 riorly, sometimes smooth, sometimes striated ; valves mostly 

 strengthened internally by a transverse posterior ridge; hinge 

 composed of a spoon-shaped fulcrum in each valve, sometimes 

 with a small tooth and a more or less developed posterior lateral 

 tooth ; ligament partly internal, partly external. 



Necera is a genus of small deep-dwelling bivalves, whose siphons, fur- 

 nished at the extremity with long tentacle-like cirrhi, protrude from a 

 characteristic posteriorly-beaked prolongation of the shell ; and the shell is 

 mostly of fragile glassy substance. The species are not very numerous, 

 but they are widely distributed throughout the seas, both of temperate and 

 tropical countries, and we have three in Britain.* The hinge has a spoon- 



* " When the only species of this genus, hitherto figured as British, was first made known, 

 our conchologists were inclined to question its indigenousness and to regard it as accidentally 

 introduced. Yet now, not only is the Necera cuspidata extant in many British collections, but 

 two other species have been added to keep it company within the last three years ; of those two, 

 one until very recently was known only in the fossil state, and both till within the last three 

 years were supposed to be peculiar to the Mediterranean. Such advances in our knowledge of 

 a genus so little known to most collectors as Necera have been due entirely to the more active 

 employment of the dredge, and the greater energy and adventure of the naturalists who have, 

 with such excellent results, kept that invaluable instrument of submarine research in continual 

 motion." — Forbes and Hanley, Brit. Moll. vol. i. p. 194. 



