MORPHOLOGY AND SYSTEMATIC POSITION OF RISSOELLA-CARIBAEA REHDER, 1943(GASTROPODA, HETEROBRANCHIA, RISSOELLIDAE)

Rissoella caribaea is one of only three known western Atlantic species of rissoellids. It was first described by Rehder (1943a,b) living amo ngst algae on the mangrove prop-roots at Bonefish Key, Lower Florida K eys, Florida. Rissoella caribaea, like other rissoellids, has a pair o f cephalic tentacles and a very distinctive (diagnostic) pair of oral lobes on either side of its bifid snout. It has a rhomboid-shaped jaw, a symmetrical radula, each row comprised of rachidian and one pair ea ch of lateral and marginal teeth. Rissoella caribaea is a simultaneous hermaphrodite, with well developed penis, vas deferens and a large po rtion of the female reproductive tract within the mantle floor This st udy supports the allocation of this species to the genus Rissoella. Ho wever, this assignment is based upon our current and very limited unde rstanding of rissoellid morphology and phylogenetics.