A Note on the British Species of Cucumarians, Involving the Erection of Two New Nominal Genera

Abstract

While preparing a report on Echinodermata from the Stilly Isles, based on collections made by the University of London Sub-Aqua Club but including also earlier records by various authors (F. W. E. Rowe,J. nat. Hist., in the Press), it became apparent that the species generally known asCucumaria saxicolaBrady & Robertson andC. normaniPace, from Mortensen's classic handbook (1927), have not been satisfactorily reassigned generically since the break-up ofCucumaria sensu extensoand need new generic names in conformity with current views on generic distinctions in the Dendrochirotida.Mortensen (1927), in his survey of the Echinoderms of the British Isles, includes seven species in the genusCucumaria: C. frondosa(Gunnerus);C. elongataDüben & Koren;C. hyndmanniThompson;C. saxicolaBrady & Robertson;C. normaniPace;C. lactea(Forbes) andC. planci(Brandt), this last species being wrongly credited to von Marenzeller.C. frondosais a plump to barrel-shaped animal with ten large, bushy tentacles, podia, at least in the older specimens, not restricted to the ambulacral areas, a calcareous ring with no posterior bifurcations on the radial plates or any fusion of the ventralmost radial and adjacent interradial plates and spicules of the body wall comprising thin, multilocular, smooth or slightly thorny plates, these being more or less restricted to the posterior region and to the podia in older animals. It has been designated type-species of the genus by Panning (1949), thus delimitingCucumaria sensu stricto. The other species included by Mortensen cannot be treated as being congeneric withfrondosaby virtue of their elongate body, ten relatively small tentacles of which the ventralmost two are smaller than the remaining eight, podia restricted to the ambulacral areas, calcareous ring showing a tendency, in some forms, to develop posterior bifurcations on the radial plates and fusion of the ventral-most radial and adjacent interradial plates and the differing form and combinations of spicules of the body wall.