100 



the mantle-lobes are united behind between siphonal orifices. M. Des- 

 hayes thinks moreover, that Lamarck's suspicion of Cardita having a byssus 

 is without foundation; Mr. Woodward especially describes the foot to be 

 grooved, spinning a byssus. The question as to the presence or absence of 

 siphonal orifices in different species remains to be determined. A list of 

 fifteen species, presumed to have the habit of spinning a byssus, are set 

 apart by the Messrs. Adams under the title originally proposed for them 

 by De Blainville, of Myt'dicardia. 



The shells of the byssus-spinning Cardita, as in the genus Area, are of 

 lighter structure than those in which there is no byssus, and in which the 

 shell is often massive, with the valves heavily and closely interlocking 

 round the ventral margin. Many of the shells are very richly variegated 

 with colour, and some are ornamented with a profusion of vaulted scales. 



The genus is widely distributed in both hemispheres, but does not reach 

 so far north as the British shores. 



1. abyssicola, Hinds. 



2. aculeata, Phil. 



3. ajar, Adams. 



4. amabilis, Desk. 



5. angisulcata, Reeve. 



6. antiquata, Linn. 



7. australis, Quoy. 



8. Belcheri, Desk. 



9. bimaculata, id. 



10. bovealis, Conr. 



11. calyculata, Brug. 



12. canaliculata, Reeve. 



13. Cardioides, id. 



14. castoruca, Desk. 



15. eompressa, Reeve. 



16. Conradi, Shutt. 



17. corbis, Phil. 



18. crassicostata, Lam. 



19. crassa, Gray. 



20. crenulata, Desh. 



21. Cumingiij id. 



22. Cuvieri, Brod. 



23. difficilis, Desh. 



Species. 



21. distorta, Reeve. 



25. elegantulus, Desh. 



26. Essingtonensis, id. 



27. excavata, id. 



28. excisa, Phil. 



29. fabula, Reeve. 



30. ferruginosa, Adams. 



31. fiabellum, Reeve. 



32. flammea, Mich. 



33. gibbosa, Reeve. 



34. Gunnii, Desh. 



35. incrassata, Sow. 



36. Jukesii, Desh. 



37. Koreensis, id. 



38. lacunosa, Reeve. 



39. laticostata, id. 



40. marmorea, id. 



41. megastropha, Gray. 



42. nmricata, Sow. 



43. nitida, Reeve. 



44. nodulosa, id. 



45. ovalis, id. 



46. pica, id. 



47. Preissii, Menhe. 



48. procera, Gould. 



49. purpurata, Desh. 



50. radula, Reeve. 



51. rostrata, Gmel. 



52. rufescens, Reeve. 



53. semen, id. 



54. Sowerbyi, Desh. 



55. spurca, Sow. 



56. squamifer, Desh. 



57. sulcata, Lam. 



58. tegidata, Reeve. 



59. teretiuscula, Phil. 



60. tricolor, Sow. 



61. tridentata, Say. 



62. tumida, Brod. 



63. umbilicata, Desh. 



64. variegata, Brug. 



65. varia, Brod. 



66. ventricosa, Gould. 



67. vestita, Desh. 



68. Zelandica, id. 



