156 



widely distributed over the globe. Including Sp/icsnia, a small species 

 partaking of the characters of Saxicava, we have only three in Britain ; 

 among the islands of the Eastern Archipelago and on the western coast of 

 South America they are more abundant, and in the latter region the genus 

 passes into the estuaries and becomes modified to the consequent difference 

 of habit. The fresh-water species have been separated from the marine 

 under the titles Potamomya and Azara. The valves of Corhula are in 

 most of the species remarkably unequal in growth, the right valve not 

 only overlapping the left one at the ventral margin, but projecting over it 

 in a most conspicuous manner at the umbo, while there is almost always a 

 peculiarly rude gibbousness of growth in the shell. The Corbula are deep- 

 dwelling mollusks, and have been little collected except by those who, like 

 Mr. Cuming and Sir Edward Belcher, have been accustomed to dredging. 

 Speaking of the British C. nucleus, it has been remarked by Eorbes and 

 Hanley that whilst the naturalist, whose efforts at collecting are confined 

 to the rocks, sands, briny pools, and streamlets of our coast, is apt to re- 

 gard the species as of unfrequent occurrence, its extreme prevalence is a 

 subject of almost perpetual complaint from the habitual dredger. 



1. adusta, Hinds. 23. 



2. sequalis, C. B. Adams. 24. 



3. sequivalvis, Phil. 25. 



4. alba, Phil 26. 



5. albuginosa. Hinds'. 27. 



6. Barrattiana, C.B. Ad. 28. 



7. bicarinata, Sow. 29. 



8. Binghami, Tart. 30. 



9. biradiata, Sow. 31. 



10. Blandiana, C. B. Ad. 32. 



11. Californica, Conr. 33. 



12. carnosa, Hinds. 34. 



13. Catlowa?, Reeve. 35. 



14 . Chitt yana, C. B. Ad. 36. 



15. contract a, Say. 37. 



16. crassa, Hinds. 38. 



17. crispa, id. 39. 



18. cuneata, id. 40. 



1 9 . decurtata, C. B. Ad. 4 1 . 



20. decussata, Desh. 42. 



2 1 . Diet ziana, C.B. Ad. 43. 



22. eburnea, Hinds. 44. 



Species. 



elliptica, C. B. Ad. 45. 



erodina, Lam. 46. 



erythrodon, id. 47. 



faba, Hinds. 48. 



fasciata, id. 49. 



fragilis, id. 50. 



fulva, C. B. Adams. 51. 



inflata, id. 52. 



Kjseriana, id. 53. 



Knoxiana, id. 54. 



Krebsiana, id. 55. 



labiata, id. 56. 



lcevis, Hinds. 57. 



inarm orata, id. 58. 



Mediterranea, Costa. 59. 



Mindorensis,^.^*2Z. 60. 



inodesta, Hinds. 61. 



monilis, id. 62. 



nasuta, Sow. 63. 



Newtoniana, C.B. Ad. 64. 



nimbosa, Sow. 65. 



nuciformis, id. 66. 



nucleus, Lam. 

 obesa, Hinds. 

 ochreata, id. 

 operculata, Phil. 

 Philippinensis, Adams. 

 princepSj id. 

 procera, Hinds. 

 rosea, Broicn. 

 rotalis, Hinds. 

 rubra, C. B. Adams. 

 Buppellii, Adams. 

 scaphoides, Hinds. 

 semen, Lam. 

 semistriata, Hanley. 

 similis, Hinds. 

 solidula, id. 

 speciosa, id. 

 sulcata, Brug. 

 Swiftiana, C. B. Ad. 

 Talieitensis, Lam. 

 tenuis, Sow. 

 trigona, Hinds. 



