Observations on Nucula Turgida Marshall and N. Moorei Winckworth

Abstract

In the course of a study of the British Nuculidae the specific characters of a large number of specimens of N. turgida and N. moorei were re-examined. It was found that no distinction could be made between the two.Examination of variation in shell colour showed that it was not possible to differentiate into two distinct types. There was a continuous graded seiies from a dark purple-grey in which the basic yellow colour was almost completely masked, through a series with decreasing numbers of purple-grey radiations, to shells in which the markings could not be differentiated as rays, and finally to shells without purple coloration. The purple-grey colour is not necessarily laid down continuously, and it does not develop until the end of the second year. As the shells get older an increasing percentage of them become coloured.Although the two types of faecal pellets described by Moore were found they could not be associated with the radiate and non-radiate shell types. The five grooved faeces that he claimed were typical of the radiate variety, were found in only three of the fifty-six specimens examined. Only one of them was from a definitely radiate shell.Shell measurements and growth rates were studied, and no feature was found on which two forms could be separated. Samples show that reproduction takes place at the same time in the rayed and unrayed shells.As the name N. nitida Sowerby is preoccupied it is suggested that the name N. turgida Marshall should now be used with N. moorei a synonym of it.