Abstract
Hemipholis cordifera is the correct name for the only known Western Atlantic species of Hemipholis. Hemipholis elon-gata, a name which has been used in place of H. cordifera, is a nomen dubium that cannot unambiguously be assigned to any known speciesof brittle star. Evidence is presented that the genus Hemipholis presently comprises only H. cordifera and its geminate Eastern Pacific congener Hemipholis gracilis, and it is shown that the latter name has priority over Hemipholis affinis. Hemipholis gracilis and H cordifera are illustrated and'compared to show how mature individuals can be distinguished. However, small individuals of both species are extremely similar. The latitudinal distributions of H. cordifera and H. gracilis appear to be causally related to coastal water temperature, possibly in conjunction with divergent ocean currents, and the relatively broad range of H. cordifera compared to H. gracilis is attributed to its cold tolerance and to the influence of widespread warm-water boundary currents in the central Western Atlantic. As regards the two other congeners that have been described, Hemipholis wallichii is revealed to be a juvenile ophiuroid incertae sedis, and Hemipholis microdiscus was previously transferred to the Amphiuridaeand assigned the nomen novum, Amphiura microdis-coida.
NSTL