Notes on Microscopic Crystals included in some minerals. Further Notes on Microscopic Crystals in some of the gems, ... With a plate. Descriptions of six new species of fresh water shells. Descriptions of three new species of exotic Unionidæ. Descriptions of twenty new species of Uniones of the United States. Descriptions of twenty-nine species of Unionidæ of the United States. Descriptions of seven new species of Unionidæ of the United States. Descriptions of three new species of Uniones of the United States. (Extracted from the Proceedings of the Academy of Natural Sciences of Philadelphia.).