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"While making a study of the scyphomedusan Atolla in north Atlantic waters I recently found that there were two species, A. wyvillei and A. vanhoffeni'. I can now state that there is a third species. Like A. vanhtiffeni, this is a small species, apparently not exceeding 30 mm. in diameter, but the shape of the base of its stomach is similar to that of A. wyvillei. Whereas A. vanheiffeni and A. wyvillei have typically 20 and 22 marginal tentacles respectively, this new species has usually 20 or 24 tentacles. It differs also from A. wyvillei in that the septa separating the rhopalar and tentacular gastral canals tend to be nearly straight and of uniform thickness, and are almost completely covered to their centripetal ends by the thin part of the coronal muscle. In A. wyvillei the septa tend to be club-shaped in appearance, diverging at their ends and extending centripetally beyond the margin of the thin part of the coronal muscle. Its range of coloration appears to be similar to that of A. wyvillei. In view of its small size, I propose to name this species Atolla parva n.sp. A fuller description will be given in a later publication, but in the meantime it is hoped that those engaged in studying plankton collections may be able to add to our knowledge of the distribution of the species."