Drulia cristinae, new species of sponge from the rio Xingu, Amazonas Basin, Brazil (Porifera: Demospongiae: Poecilosclerida: Metaniidae Volkmer-Ribeiro, 1986)

ABSTRACT. A recent survey of the aquatic fauna in the rio Xingu, Pará State, Brazil, revealed a new species of Drulia Gray 1867, an extraordinary genus of freshwater sponge endemic to South America. Drulia cristinae n. sp. is distinguished in part by having gemmoscleres typically with elliptical outline and outer face with small, central crest or irregular bulge (exceptionally nude), oscules set atop conical projections of skeleton, and microscleres minute, wholly nanospined amphioxea. A taxonomic key is presented for the six species now composing the restored and redefined genus Drulia: D. brownii, D. cristata, D. uruguayensis, D. conifera, D. ctenosclera and D. cristinae n. sp. Furthermore, the monotypic South American genus Houssayella is retained as valid in Spongillidae on the basis of sharing gemmoscleres with true birotulate pattern (i.e., symmetrical disks separated by short or long, spiny or smooth shaft).