Sclerosponges, Pharetronids, and Sphinctozoans (Relict Cryptic Hard-Bodied Porifera) in the Modern Reefs of Enewetak Atoll

Several sclerosponge and related species occur sparingly within modern reefs of Enewetak (formerly Eniwetok) Atoll in the central Pacific Ocean. Ranging over 4-35 m depths, the sclerosponges occupy both the outer reef wall and lagoonal coral knolls at Enewetak. The species encountered are described as seen in standard paleontologic preparations; these forms can thus be readily compared with various important fossil groups. The sclerosponge Acanthochaetetes wellsi is of finely tubular construction, the sclerosponge Astrosclera willeyana is densely labyrinthine, the pharetronid Murrayona phanolepis appears more openly labyrinthine, and the sphinctozoan Vaceletia crypta consists of successively stacked hemispherical shells.