A new species of Exosphaeroma stebbing (Crustacea : Isopoda : Sphaeromatidae) from the Pacific coast of Mexico

Exosphaeroma bruscai is described from the Pacific coast of Mexico. Exospha eroma bruscai is most closely related to E. diminuta Menzies & Frankenberg, 1966 from the western Atlantic, from which it differs in having much longe r antenna, an acute rostrum, a triangular first pleopod endopod, a transver se suture on exopod of pleopods 3-5, and a considerably longer and more sle nder appendix masculina. Specimens examined here define the geographic dist ribution of E. bruscai from the central Gulf of California to Los Arcos, in the southern part of Banderas Bay, Jalisco. Previously published records o f an unidentified Exosphaeroma from the eastern tropical Pacific indicate t hat E. bruscai occurs from sandy beaches of the upper Gulf of California to Colombia.