Original Description: Anodonta trapsialis Lamarck, J.B. 1819. Histoire Naturelle des Animaux sans Vertebres. VI, p 87.
Type Locality: dans les eaux douces etrangeres a celles de l’Europe?
Holotype: Location unknown.
For Synonymy see: Simone, L.R.L. de. 1994. Anatomical characters and systematics ofAnodontites trapesialis (Lamarck, 1819) from South America (Mollusca, Bivalvia, Unionoida, Muteloidea). Studies on Neotropical Fauna and Environment 29(3):169-185.
Description: “Shell strongly oblique, subovate to subtrapezoidal, narrowly rounded, or bluntly pointed behind. Epidermis shining, only here and there, and not always, with scalariform radial bands of wrinkles. Prismatic border narrow and of equal width.
A rather well defined group, distinguished also by the large and comparatively thin shell: the largest species of the genus belong here. Usually we discover that the valves are gaping anteriorly, and sometimes also posteriorly. Whether this is connected with the anatomical structure, or with habits, is not known. There is hardly a question that the genus Leila is descended from forms belonging to this group.” (Ortmann, 1921:621).
Specimens Examined: INHS 14914 (1). Caño, Lat 7 degrees, 16.26 N, long 71, 5.20 W, Apure, Venezuela. 6 January 1992. L.M. Page, et al. INHS 14913 (1). Caño Caicara, 2 km N La Ye, Apure, Venezuela. 23 January 1993. L.M. Page & D.C. Taphorn. INHS 14807 (6). Caño Masparito, 1 km NW Libertad, Barinas, Venezuela. 14 January 1993. K.S. Cummings & C.A. Mayer. INHS 14905 (1). Caño Hondo, Agua Negra, Barinas, Venezuela. 14 January 1993. K.S. Cummings & C.A. Mayer. INHS 14866 (19). Caño el Sardinero, 14 km SE Guanare, Portuguesa, Venezuela. 1 January 1993. K.S. Cummings & C.A. Mayer. INHS 14945 (23). Caño El Sardinero, 14 km SE Guanare, Portuguesa, Venezuela. 2 January 1994. K.S. Cummings & C.A. Mayer. INHS 14930 (1). Caño Igues, La Capilla, Portuguesa, Venezuela. 3 January 1994. K.S. Cummings & G.B. Mottesi. INHS 14957 (2). Rio Guanare, Puerto Animas, Portuguesa, Venezuela. 1 January 1994. K.S. Cummings & C.A. Mayer.