New species of Heterodrilus (Oligochaeta, Tubificidae) and records of H-maiusculus from the Mediterranean Sea

The exclusively marine genus Heterodrilus is common in sandy sediments, par ticularly in tropical and subtropical seas. In this paper, H. maiusculus, p reviously known only from Saudi Arabia, is recorded from Corsica and Italy, and it is shown to have bifid penial chaetae, a trait confirmed also for p aratypic and topotypic material of the species. Two new species are describ ed: Heterodrilus urlae sp.n. and H. tripartitus sp.n., both from Italy. Het erodrilus ursulae has trifid anterior chaetae, short, characteristically be nt and bipartite atria, and long spermathecal ducts; H. tripartitus has bif id anterior chaetae and spermathecae with distinct vestibules, the latter f eature being unique within the genus.