Apedinella radians (Lohmann) Campell. Cells are apple-shaped (7-10.5 microns wide, 6-9.5 microns long) with a single flagellum bearing mastigonemes emerging from an apical pit. Cells are radially symmetrical with six peripheral chloroplasts, each with a prominent pyrenoid on the innerside. The nucleus occupies a central position in the cell and is roughly spherical. Mitochondrial profiles run longitudinally through the cell between the chloroplasts, coalescing anteriorly to form one large mitochondrial reticulum which encircles the apical pit. In the anterior region of the cell the mitochondrial reticulum is closely associated with the filamentous cytoskeleton. A single dictyosome is located at the posterior region of the cell. The cells have two scale types: ovoid body scales and elongate spine-scales. The ovoid scales are of two size classes (0.6-0.8 x 0.4-0.5 microns and 1.5-2 x 1.1-1.3 microns) and cover the entire cell. Cells also bear six slender spine-scales, (9-13 microns long) which, according to Throndsen, are cellulosic. The spine-scales are evenly distributed around the lateral circumference and have their attachment points between the chloroplasts just anterior to the equator of the cell. Each spine-scale has a triangular base bearing a long tapering spine. The proximal side is concave with a central evagination at the base to which is attached an extracellular striated fibrous connector or micro ligament. The other two points of the triangular base appear to rest on the cell surface, that is, the covering of ovoid body scales. The microligament attaches the spine-scale to the plasma membrane. Plaques are located beneath the areas where the micro ligaments contact the plasma membrane. Each plaque consists of two discrete electron dense plates, the innermost being the thinnest, and has the following dimensions: height 0.25 microns, length 0.39 microns, width 0.07 microns The distal face of each plaque is somewhat concave following the contours of the plasma membrane.