The Tribe Alasmidontini (Unionidae, Anodontinae), Part I: <i>Pegias</i>, <i>Alasmidonta </i>and <i>Arcidens</i>

Abstract

The taxonomy, morphology, life history, and distribution of fourteen species, comprising four traditional genera, are described. Discussions of morphology include descriptions of the shell, anatomy, and glochidium (where possible) of each species and of character variation, together with statistical tables, illustrations, and scanning electron microscope photographs. Distributional data include organized lists of all museum material, with distribution maps, and with special reference to recently collected specimens that are likely to represent living populations. Also discussed are some quantitative effects of water hardness and temperature on shell weight and on characters linked with shell weight, new glochidial characters as observed with the scanning electron microscope, the indirect determination of sex in non-gravid specimens by examination of the demibranchs (Ortmann's method), and taxonomic relationships of the Tribe Alasmidontini. Species recognized are: Pegias fabula (Lea), Alasmidonta {Pressodonta) viridis (Rafinesque), A. (P.) heterodon (Lea), A. (Alasmidens) mccordi Athearn, A. {Alasmidonta) undulata (Say), A. (A.) arcula (Lea), A. (A.) wrightiana (Walker), A. (Decurambis) marginata Say, A. (D.) atropurpurea (Rafinesque), A. (D.) raveneliana (Lea), A. (D.) varicosa (Lamarck), A. (/).) robusta (new species), Arcidens (Arkansia) wheeleri (Ortmann and Walker), and A. {Arcidens) confragosus (Say). A new subgenus, Alasmidens, is described.