Redefinition of Teneridrilus Holmquist (Oligochaeta: Tubificidae), with description of two new species from North America

The tubificid genus Teneridrilus Holmquist, 1985 (subfamily Tubificinae) is redefined. The genus was originally monotypic for the type species, formerly classified as Ilyodrilus mastix Brinkhurst, 1978. The genus now includes Teneridrilus columbiensis, a new combination for Isochaetides columbiensis, and two new species. The first of these, Teneridrilus calvus, is described by Erseus and Brinkhurst, and the second, Teneridrilus flexus, by Erseus and Hiltunen. Synapomorphies for the genus are strongly modified chaetae in II and an enlarged eversible pharnyx. The genus is distributed from China to British Columbia, Washington and California in freshwater near the mouths of large rivers, and in the St. Marys River, which connects Lake Superior with Lakes Michgan and Huron.