title: Helicoplacoidea: A New Class of Echinoderms.
abstract: A fusiform, spirally coiled and pleated, free-living, heavily placate echinoderm with an expansible test has been discovered in the Lower Cambrian Olenellus zone of California. It is characterized by 10 "interambulacral" areas, a single principal endothecal ambulacrum with a short branch, and oral and apical regions at opposite poles. A new class, the Helicoplacoidea is proposed for the new genus Helicoplacus, with two new species, H. gilberti (type species) and H. curtisi.
authors.forename: J W
authors.initials: JW
authors.lastname: Durham
authors.forename: K E
authors.initials: KE
authors.lastname: Caster