The authors of this volume study and describe the valve morphology of 108 taxa, representing 75 distinct species, in the genera Amphora and Halamphora from aquatic environments in the United States and Japan. Amphora Ehrenberg ex Kützing and Halamphora (Cleve) Levkov are taxonomically diverse genera of raphid diatoms. In addition to being species rich, their ecology is equally diverse, with representatives of the genera present in coastal and inland waters from the tropics to the arctic. Of the 75 species, nearly one-half of them (33) are described as new, including 4 from the genus Amphora and 29 from the genus Halamphora. Eight species are transferred from Amphora to Halamphora and new combinations proposed. All taxa considered herein have been cultured, and 4 genes (the nuclear encoded 18S and 28S rDNA and the chloroplast encoded rbcL and psbC genes) have been sequenced for each. This combination of morphological and molecular data lays an important foundation for future research of the taxonomy, ecology and systematics of the Amphora and Halamphora floras of coastal and inland waters. Skryť popis