AGLAOTHAMNION HALLIAE COMB-NOV AND A-COLLINSII SP-NOV (CERAMIALES, RHODOPHYTA) - RESOLUTION OF NOMENCLATURAL AND TAXONOMIC CONFUSION

Specimens from the exsiccatae Phycotheca Boreali-Americana number 698 are shown to represent two distinct species. One of them, formerly kno wn as Callithamnion halliae, is transferred to Aglaothamnion on the ba sis of its uninucleate cells. The specimens exhibit distichous branchi ng and are ecorticate. A lectotype is proposed for one of the P.B.-A # 698 specimens displaying these characters. Aglaothamnion halliae (Coll ins) comb. nov. is an earlier name for Aglaothamnion westbrookiae Ruen ess et L'Hardy-Halos. The second species, together with specimens of P .B.-A. #1896, has radial branching and corticated axes and is describe d herein as a new species, Aglaothamnion collinsii. The binomial Aglao thamnion boergesenii (Aponte et Ballantine) L'Hardy-Halos et Rueness i n Aponte, Ballantine, et J. Norris is validated. A key to the tropical and warm-temperate western Atlantic species of Aglaothamnion is prese nted.