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Abstract
Specific diagnostic characters are reviewed and redefined for the genus Polymastia in northern New Zealand waters, to provide a framework for the recognition of new species, and for the revision and redefinition of other Polymastiidae. Eight new species of Polymastia are described, and Polymastia fusca Bergquist, P. hirsuta Berquist, and P. cf. massilis Carter are redescribed in the light of new material. Species of Polymastia which contain exotyles and centrotylote oxea in addition to the usual megasclere complement, provided the opportunity to redefine the polymastid genera Proteleia, and Tylexocladus, which would typically have been reserved respectively, for sponges with these spicules. Anew species of Tylexocladus is described from the Chatham Rise in southern New Zealand, providing a first record of the genus from this location. A new genus Acanthopolymastia is established for southern ocean Polymastiidae with acanthose centrotylote oxea, with Atergia acanthoxa Koltun from Antarctica as the type species. Two additional species from New Zealand and the Norfolk Ridge, New Caledonia are described, and all are compared to Atlantic species of the same genera. Suggestions for partitioning of shallow‐water Polymastia species are put forward.
