Walker, Frierson, and Simpson (in part) believe this to be a _Pleurobema_, and not a _Lampsilis_ (see also Simpson, ’00, p. 557, and ’14, p. 131), and this comes nearest to the truth, in fact, it is the most plausible assumption to be made from the study of the shell alone. The shell “resembles a very elongated _Quadrula coccinea_,” according to Meek and Clark, and the comparison with _Pleurobema argenteum_ and _breve_ (which, by the way, are synonyms), made by Simpson, is significant. We must keep in mind that Call’s fig. 4 represents the normal shape of the shell, while his fig. 1 is rather abnormal, and possibly does not belong here at all. These two figures by no means represent the female and male, as Call believes. The investigation of the soft parts has shown that this actually is a _Fusconaia_. Corresponding, both in soft parts and shell, to the _barnesiana_-type of the upper Tennessee region. _F. ozarkensis_ differs from _barnesiana_ by the more elongated (subtrapezoidal) outline of the shell, more anterior beaks, and the weak development of the rays, which are faint at the best, and often entirely absent. A swollen form of it is not known to me, but specimens from White River are slightly more convex than those from James River (farther up). Also Utterback’s quotation of Frierson (p. 87, footnote) make it probable that there are differences in obesity. ANATOMY. _Supraanal_ opening probably separated from the _anal_ by a short mantle-connection, but in all my specimens this is torn by rough handling. Inner lamina of inner gills free from abdominal sac. All four gills marsupial in the female. _Placentae_ well developed and _subcylindrical_. Anal opening with small papillae, branchial opening with well developed papillae. _Palpi_ as usual, their posterior margins connected for about one third of their length or less. As to the color of the soft parts, which is so characteristic in _barnesiana_, not much can be said, since my material has been too long in alcohol. But in most of my specimens the gills are yet distinctly suffused with black. The placentae have been rendered whitish, but here and there traces of a dark stain are preserved (which is disappearing gradually). It is quite possible that the color of the placentae originally was similar to that of _barnesiana_. The _glochidia_ are subelliptical, slightly higher than long; L. O. 15, B. O. 18, thus agreeing with those of _F. barnesiana_. NOTE ON THE RELATION OF SNAIL FAUNA TO FLOODS. BY A. RICHARDS.