Phascolosoma nigrescens (Keferstein, 1865)

Physcosoma horsti ten Broeke, 1925:89.

Physcosoma minutum ten Broeke, 1925:87.

Physcosoma nigrescens Keferstein, 1865:424 .

Physcosoma varians Keferstein, 1865:424 –426. – ten Broeke 1925:85.

Remarks. Members of the Phascolosomatidea possess a dorsal nuchal organ surrounded by the tentacles and lack a dorsal shield. There are no contractile vessel villi, the introvert is less than twice the body length, and the hooks lack basal spines in the genus Phascolosoma . P. nigrescens is recognized by its numerous rings of hooks (usually more than 100 complete and incomplete rings) and the hooks have a minutely scalloped base and a clear streak with an expansion near its midpoint.

Distribution. ten Broeke (1925) reported this species from several sites in Venezuela identifying it as four different species. It was collected from Caracas Bay, Spaansche Water, and Spaansche Haven in Curaçao. P. nigrescens is considered a circumtropical species from shallow waters the Indian, Pacific and Atlantic Oceans.