BIOTIC CENSUS OF CAPE COD BAY: HYDROIDS

Abstract

1. Twenty-five species of hydroids were identified in samples taken during the Biotic Census of Cape Cod Bay. Of these, only Corymorpha pendula, Acaulis primarius, Hydractinia echinata, Gonothyraea loveni, Sertularia cupressina, and S. latiuscula were particularly common. Eleven of the 25 species were found only once or twice. Bottom type throughout much of the bay is sand or silty-sand, and the general paucity of firm substrates is evidently a primary factor limiting hydroid abundance and diversity in the area. 2. Eleven species are recorded from Cape Cod Bay for the first time. Present records extend the known distribution of Euphysa farcta and Acaulis primarius southward, and that of Stylactis arge and Lovenella gracilis northward. As expected, the hydroid fauna of Cape Cod Bay is characteristically boreal in its zoo-geographic affinity, and many of the species represented are amphi-Atlantic. 3. Halecium gracile Verrill, 1874 is placed in synonymy with H. halecinum (Linnaeus, 1758), Tubularia cristata McCrady, 1857 is regarded as a synonym of Ectopleura dumortieri (van Beneden, 1844), and Tubularia crassa Fraser, 1941 is synonymous with Corymorpha pendula L. Agassiz, 1862.