A REEXAMINATION OF SOME SPECIES OF AMPELISCA (CRUSTACEA: AMPHIPODA) FROM THE EAST COAST OF NORTH AMERICA

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Abstract
Ampelisca verrilli n. sp. occurs from the intertidal to 50 m from southern Cape Cod to at least North Carolina. Individuals from North Carolina are small and slightly divergent in morphology from those from Massachusetts. A. macrocephala Liljeborg, with which A. verrilli has been confused for many years in New England, is figured. It occurs from just south of Cape Cod north, and from Nova Scotia north overlaps the range of A. eschrichti Krøyer. A. agassizi (Judd) (formerly known as A. compressa) is redescribed. Its range in the east is from Nova Scotia to the Caribbean at shallow inshore depths to 450 m. Eastern populations are closely similar to those from the eastern Pacific. A. declivitatis n. sp., which has been confused with A. spinimana Chevreux, is known from west of Greenland to the middle Atlantic States at lower continental shelf to bathyal depths, overlapping the range of A. agassizi on the continental shelf and the ranges of deep-sea species well down the continental slope. Parasitic worms, probably neorhabdocoele Turbellaria, occur in A. declivitatis. The incidence of intersexuality is high, but it does not appear to be related to parasitism by Turbellaria and may result from a polygenic-hormonal sex determination mechanism. A key is provided to the 24 species of Ampelisca known or suspected from eastern North America.