MORPHOMETRY AND TAXONOMY OF HEXACONTIUM SPECIES FROM WESTERN NORWEGIAN FJORDS

A morphometric approach has been used, for both plankton and surface s ediment samples, to map the size distribution of the polycystine radio larian Hexacontium pachydermum Jorgensen in two western Norwegian fjor ds, Sognefjord and Hardangerfjord. We have recognized that H. pachyder mum, as defined by Jorgensen (1900), has two morphotypes which occupy two different size clusters. These clusters do not overlap and we have suggested, therefore, that they represent two different species, the smaller of the two is the original H. pachydermum, while the larger mo rphotype is described as H. gigantheum n. sp. Anew form, H. hostile fo rma A is also described.