Donax Linnaeus 1758

DICHOTOMOUS KEY TO BRAZILIAN DONAX LINNAEUS, 1758, ADAPTED FROM LIMA & MARQUES (PERS. COMM.) 1. Nodular posterior surface ............................................................................ Donax hanleyanus Philippi, 1847 — Non-nodular posterior surface ..................................................................................................................... 2 2. Evenly rounded posterior ridge .................................................................................................................... 3 — Carinate posterior ridge with an angle ......................................................................................................... 4 3. Concave or flat ventral margin, trapezoid shape .......................................................... Donax trapesialis n. sp. — Convex ventral margin, subglobose shape .................................................... Donax gemmula Morrison, 1971 4. Visible growth lines, punctuated .............................................................. Donax denticulatus Linnaeus, 1758 — Imperceptible growth lines .......................................................................................................................... 5 5. Strongly triangular, sharp posterior ridge ......................................................... Donax striatus Linnaeus, 1767 — Moderately triangular, wide, unevenly rounded posterior ridges, two posterior slope surfaces easily distinguishable ........................................................................................................... Donax vellicatus Reeve, 1855