Varichaetadrilus angustipenis is a freshwater oligochaete originally described as 'Limnodrilus angustipenis from material collected by J.K. Hiltunen from Saginaw Bay, Lake Huron. It was assigned to the genus Varichaetadrilus by R. O. Brinkhurst in 1989. This rarely collected species presently is known to occur in Alabama, Illinois, Louisiana, Manitoba, Michigan, North Carolina, New Brunswick, New Jersey, Ohio, Ontario, and Tennessee (Coates and Wetzel, manuscript in prep.). In 1980, it was collected in the San Francisco Estuary Delta, near Shermans Island, It occurs upriver to the Sacramento Turning Basin. Oligochaetes lack parapodia and have relatively short setae. A major feature of this species is an unusually long penis sheath. They are hermaphroditic, with a few anterior segments modified to form a reproductive section, called the clitellum. At sexual maturity, they have a few modified segments forming a reproductive section, called a clitellum. Specimens of V. angustipenis were 10-15 mm, and had 25-60 segments. The worms copulate and lay fertilized eggs in cocoons. Marine oligochaetes usually occur in silty or muddy sediments and are deposit-feeders.
https://mjwetzel.inhs.illinois.edu/research/freshwater-oligochaetes/