Abstract
A total of 121 photographs was made of specimens in the tintinnid genus Ptychocylis, collected in the vicinity of Tromsö, northern Norway. Selections are shown from these photographs to illustrate variations that occurred. In addition, detailed measurements were undertaken of 165 specimens from the same samples. From all of these and from the literature it is concluded that it is not feasible on the basis of lorica shape to distinguish among the following described species: P. acuta, P. arclica, P. basicurvaia, P. cylindrica. P. drygalskii, P. glacialis and P. obtusa. Furthermore, some of the illustrated forms do not correspond to any descriptions found in the literature. It is concluded either that there is one multivariate species encompassing the above list, by priority to be named P. obtusa, or else that other means than the lorica alone must be used to distinguish species in this genus.

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