CONTENTS. 



Description of New Species of the Family Unionidsc. Read March 5, 1852, . . Page 9 



Do of a New Genus of the Family Melaniana, and New Species of Melania;, 



Read March 5, 1852, ......... 51 



Do of a New Species of Helix from California, Read March 5, 1852, . . 59 



