1 12 Retrospect of the Shells of Essex County. 



74. Margarita obscnra, 253. f. 171.* 



73. Margarita undulata, Sowerby, 254. f. 172.* 



53. Mesodesma arctata, 57. f. 39. 



75. Modiola discrepaus, Montagu, 129. f. 83. 

 61. Modiola modiolus, Turton, 123. 



61. Modiola plicatula, Lam., 125. f. 81. 



61. Mytilus edulis, Linnceus, 121. f. 82. This, though 



a very common shell, yet not devoid of beauty, 

 especially in the varieties, of which M. pellucidus 

 of Pennant and others, is most distinguished as 

 noticed in Number II. p. 62, where dele the name, 

 as a distinct species. 



62. Mytilus pellucidus, variety of Mytilus edulis. 122. 

 51. Mya arenaria, Linnccus, 40, 



67. Natica clausa, Broderip and Sowerby, 238. f. 167. 



67. Natica heros, Say, 231. f. 163. Dr. Gould gives 



an interesting account of its habits. 



67. Natica triseriata. Say, 233. f. 165. 



58. Nucula limatula, Say, 98. f. 62. 



58. Nucula minuta, Turton, 101. 



58. Nucula myalis, Couth., 99. 



54. Pandora trilineata, Say, 44. 



62. Pecten magellanicus, Lam., 132. 

 47. Pectinaria Belgica, Lam., 7. 



55. Petricola pholadiformis, Lam., 63. 



50. Pholas crispata, Linnaus, 27. Found living in a 



young state at Phillips' beach, Lynn, as noticed 

 on p. 50, (No. II.) under the name of Pholas lamel- 

 lata, Turton, which latter, dele. 



69. Purpura Lapillus, Lam. } 301, also variety imbrica- 

 ta, 302. 



74. Pyramis striatula, Couth., 269. f. 174. 



74. Rostellaria occidentalis, Beck, 298. f. 205. 

 54. Sanguinolaria fusca, Conrad, 66. f. 42. 

 54. Sanguinolaria sordida, Couth., 67. 



54. Saxicava distorta, Say, 61. f. 40. 



75. ScalariaGrsenlandica, Chemn> 249. f. 170.* 



51. Solen eusis, Linn&us, 29. 



