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.
