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at the extremities, and furnished with numerous serial and entering teeth- 

 Ligament wholly external. 



A. tortuosa, A. sulcata, 



' semitorta, ' ovata, 



' Nose, ' barbata, 



' tetragona, ' fusca, 



4 umbonata, ' Magellanica, 



' sinuata, ' Domingensis, 



' avellana, ' lactea, 



' cardissa, ' trapezina, 



' ventricosa, ' pistachia, 



' retusa, ' pisolina, 



A. cancellaria, 

 ' callifera, 

 ' irudina, 

 ' Ilelbingii, 

 ' scapha, 

 ' antiquata, 

 ' rhombea, 

 ' granosa, 

 ' auriculata, 



A. inequivalvis, 

 ' Indica, 

 ' senilis, 

 4 Brasiliana, 

 ' corbicula, 

 1 squamosa, 

 ' Cayennensis, 

 ' bisulcata, 



9 fossil species. 



Pectunculus. Shell orbicular, almost lenticular, equivalve, subequilat- 

 eral, close; hinge arched, furnished with numerous serial, oblique, entering 

 teeth; those in the middle obsolete, nearly obliterated. Ligament external. 



P. glycimeris, 

 ' pilosus, 

 4 undulatus, 

 ' marmoratus, 

 ' scriptus, 



P. pennaceus, 

 4 rubens, 

 ' angulatus, 

 ' stellatus, 

 ' pallens, 



P. violacescens, 

 ' zonalis, 

 ' striatularis, 

 ' nummarius, 

 ' castaneus, 



P. pectinatus, 

 ' pectiniformis, 

 ' radians, 

 4 vitreus, 



9 fossil species. 



Nucula. Shell transverse, ovate, triangular, or oblong, equivalve, inequi- 

 lateral; no facet between the beaks; hinge linear, broken, many toothed, in- 

 terrupted in the middle by an obliquely extending spoon-shaped pit; the teeth 

 numerous, often produced, as in the pectens; the beaks contiguous, curved 

 backwards. Ligament marginal, and partly internal, inserted in the pit or 

 spoon of the hinge. * 



N. lanceolata, 





N 



Nicobarica, 



N. margaritacea, N. glacialis, 



' rostrata, 





c 



obliqua, 



' tellinoides, 4 fossil species. 



' pella, 













^. lanceolata, (Sowerby 



f.l. 





N.Fabula, (Sowerby, C. 111. f. 13. 



' elongata, ' 







2. 





' Elenensis, ' 14. 



4 tellinoides, ' 











' cuncata, ' 15. 



4 crenifera, ' 







3. 





4 striata, ' 16. 



' arctica, ' 







4. 





' Mauritiania, ' 17. 



' Nicobarica, ' 







4. 





' limatula, (Say, Am. C. t. 12. 



4 curvirostra, ' 







5. 





' lsevis, ' 12. 



« Pella, ' 







9. 





' concentrica, ' 12. 



' glacialis, (Wood, 



Supp. 



pi. ii. 



f. 6. 



' margaritacea, (Sowerby, Gen. 



' fluviatilis, (Sowerby, 



Gen. 





' decussata, C. 111. f. 18. 



4 minuta, (Montague. 









' rugulosa, ' 19. 



' para, (Sowerby, 



C. 



Ill 



. f. 7. 





' nitida, ' 20. 



4 costellata, ' 







8. 





' obliqua, ' 21. 



4 gibbosa, ' 







9. 





4 tenuis, (Montague, 



4 eburnea, ' 







10. 





4 convexa, (Sowerby, C. 111. f. 22. 



' polita, ' 







11. 





' Pisum, ' 23. 



' nasuta, ' 







12. 





' exigua, ' 24. 



