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Five new species of poecilosclerid sponges, Artemisina amlia sp. nov., Coelosphaera oglalai sp. nov., Melonanchora globogilva sp. nov., Tedania kagalaskai sp. nov., and Mycale carlilei sp. nov, are described from the Aleutian Islands, Alaska, from depths ranging between 100–190m and are compared with congeners of the North Pacific Ocean.Keywords: Taxonomy, Porifera, Demospongiae, Poecilosclerida, new species, N-Pacific, Aleutian Islands, Alaska

A modified type of kinocilia has been found in the Aulophora-Iarva of the sedentarian polychaete Lanice conchilega. For this newly described cilium type the term "discocilium" is proposed. The only structural difference from usual locomotory cilia is the tip, which possesses a discoidal head. The head is formed from the terminal part of the cilium shaft, which is bent to give rise to a loop-like ring covered by the ciliary membrane. Three types of discocilia can be distinguished: a) discocilia having swollen, bulblike heads with a central straight axoneme; b) discocilia having heads with a curved lateral axoneme and c) discocilia in which the axoneme forms a loop. The internal structure shows the usual 9 + 2 arrangement of the filaments. The head shows no sign of secretion; it appears structureless in electron microscopical examination. There are two kinds of discocilia arrangements: 1) isolated bunches of cilia especially at the tentacles and in the frontal region, and 2) segmental dorsal rows of cilia. The possible formation of discocilia is described.

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Plakina tanaga and Plakina atka n. spp. are described from the waters around the Aleutian Islands at depths between 118 and 146m. These are the first records of the genus from the Aleutian Islands. The new species described here are compared with the six species of Plakina previously reported from the Pacific. Both species belong to the Plakina trilopha species-complex and differ from other Pacific species of Plakina in their conspicuous convoluted surface pattern, color, and spiculation. In addition to the usual set of triods both species have a second category with basally spined rays. Plakina tanaga n. sp. has a strongly convoluted, microtuberculate surface, and a few small, thin spines at the basal rays of the triods, and relatively large trilophose calthrops. Plakina atka n. sp. has a smoother surface, more numerous larger and thicker basal spines at the triods, and considerably smaller lophocalthrops which are tetralophate.