4 NEW SPECIES OF PYRAMIMONAS (PRASINOPHYCEAE) FROM ARCTIC CANADA INCLUDING A LIGHT AND ELECTRON-MICROSCOPIC DESCRIPTION OF PYRAMIMONAS-QUADRIFOLIA SP-NOV

A preliminary survey of the marine nanoplankton of Northern Foxe Basin , Canada, based on observations of field material and crude cultures, has revealed nine species of Pyramimonas. Only two of these (P. nansen ii and P. orientalis) have been reported previously, P. nansenii from Greenland and Denmark and P. orientalis from many parts of the world. In this paper we describe, using light and electron microscopy techniq ues, a species obtained in culture, Pyramimonas quadrifolia sp. nov. P yramimonas quadrifolia is unique in scale morphology and flagellar roo t structure but otherwise displays characters typical of the subgenus Vestigifera. During division of the chloroplast, a structure similar t o the ''plastid-dividing (PD) ring'' was observed. We also report on t hree new species known only from EM whole mounts of field material: Py ramimonas aurita sp. nov., Pyramimonas dichotoma sp. nov. and Pyramimo nas igloolikensis sp. nov. Pyramimonas sp. is only known from its larg e body scales.