Encyonema norvegicum

Valves moderately dorsiventral with moderately rounded apices. Dorsal margin moderately arched, with most prominent dorsal arching at the lower limits of the valve size range. Ventral margin slightly tumid or slightly concave at valve center, giving the margin a slightly triundulate or biundulate appearance. Axial area narrow and central area asymmetric, with a slightly or moderately rounded central area on the dorsal side of the valve. External areolae generally dumbbell shaped, but may be bent into V- or Y-shapes, especially at the valve center. Striae slightly radiate at valve center and becoming parallel, or slightly convergent near the apices. Internally, alveoli formed by connected rectangular openings resembling a string of beads. Transapical costae are broad and not prominent. Raphe very slightly dorsally displaced with dilated external proximal raphe ends. Internally, proximal raphe ends strongly curved dorsally and raphe terminating distally in a small helictoglossae.