155 



shaped fulcrum, with an external ligament passing internally into it; on 

 the posterior side it is sometimes strengthened with teeth, and in a few 

 instances with an over-arching ridge. One species from the China Seas, 

 N. rostrata, of which we have given a figure, is remarkable beyond all the 

 rest for its size and thickness. 



1. abbreviata, Forbes. 



2. alternata, D'Orb. 



3. attenuata, Forbes. 



4. casta, Hinds. 



5. Cleryana, D'Orb. 



6. cochlearis, Hinds. 



7. conciuna, id. 



8. costata, Sow. 



9. costellata, Desk. 



Species. 



10. cuspidata, Oliv. 



11. didyma, Hinds. 



12. elegans, id. 



13. fragilis, Adams. 



14. Gouldiana, Hinds. 



15. hyalina, id. 



16. iridescens, id. 



17. lata, id. 



18. Moluccana, Ad. Sf Bv. 



19. nitida, Ad. 8p Rv. 



20. ornatissmia, D'Orb. 



21. opaliua, Hinds. 



22. Pkilippinensis, id. 



23. rosea, id. 



24. rostrata, Ghemn. 



25. Singaporensis, Hinds. 



26. trigona, id. 



Figures. 



Ne^era cuspidata. PI. Q. Pig. 2. Shell, with animal, showing the 

 tentacle-like cirrhi on its siphons, protruding from the beaked pos- 

 terior extremity of the shell. 



Ne^era rostrata. PI. 41. Pig. 221. Shell, showing the beaked pos- 

 terior extremity. 



Genus 9. CORBULA, Bruguiere. 



Animal ; short, with the mantle closed except in front, for the 

 passage of a rather large foot ; siphons very short, united, with 

 the orifices fimbriated ; anal siphon with a 'protruding tubular 

 membrane. 



Shell ; inequivalve, globose or oblong, mostly very thick and solid, 

 and more or less beaked or angularly produced posteriorly ; left 

 valve generally the smaller ; hinge composed of a solid subre- 

 curved central tooth in one or both valves, with corresponding 

 pits, and a deep) pit on one side containing the ligament. 



Closely allied to the Necera, but with very solid and often richly- coloured 

 shells, are the Corbulce, a group more numerous in species, and even more 



