CONTENTS OF Mr LEA'S MEMOIR. 



Page 



Description of Freshwater and Land Shells. Read December 19, 1834. , ... 1 



Continuation. Read January 2, 1835. ........ 19 



Do. Read September 18, 1835 21 



Do. Read February 5, 1836 23 



Do. Read July 15, 1836 48 



Do. Read August 19, 1836 69 



Do. Read November 4, 1836 73 



Do. Read July 21,1837 95 



Do. Read January 5, 1838 103 



Do. Read January 19, 1838 108 



Systematic Index of the Family Naiades. . . . . . . . . 110 



Synopsis of the Family Naiades. ..... . . . 113 



Division of the Family Naiades. . ... . . . . . 118 



Genus Margarita. . . . . . . . . . , 121 



Subgenus Unio. , . . . . . . . . . . 121 



Subgenus Margaritana. . . . . . . . . . 134 



Subgenus Dipsas. ........... 136 



Subgenus Anodonta. . . . . ... . • . 137 



Genus Platiris. ............ 141 



Subgenus Iridina. .......... 141 



Subgenus Spatha. . . . . . . . . . .141 



Addenda. 143 



Geographical Distribution of the Species of tlie Family Naiades. .... 145 



Genus Margarita. ........... 145 



Subgenus Unio. . . . . . . . . . . .145 



Subgenus Margaritana. . . . . . . . . . . 148 



Subgenus Dipsas. . . . . . 149 



Subgenus Anodonta. . . . . . . ■ , . . . 149 



Genus Platiris. 150 



Subgenus Iridina. ........... 150 



Subgenus Spatha. . . . . . . . . . . .150 



List of Authors. . 152 



2 N* 



