Northwestern Pacific ascidians (Tunicata: Ascidiacea). Part 2. Order Phlebobranchia

A taxonomy of phlebobranch ascidians from the NW Pacific coasts of Russia, including Bering Sea, Sea of Okhotsk and northern part of the Sea of Japan, is presented.Order Phlebobranchia currently comprises 8 families, 5 of which are represented in the region.Twenty-three species and 11 genera are recognized as valid in the region.Four new species are described: Chelyosoma tranlucidum sp.n., Ascidia beringia sp.n., A. kurila sp.n. and A. vivipara sp.n.All species known in this region are included and most of them redescribed based on newly collected specimens and/or on museum material.Identification keys and quality photographic images are provided to simplify a task of species identification for a wide range of biologists.Special attention is paid on nomenclature of discussed families, genera and species, a subject that received little attention from most ascidian experts previously.