Zoœcia strongly pyriporiform, very small, length about ·4 mm.; areas broadly speaking elliptical but with a strong tendency to have the upper end flattened rather askew to the central line, average length ·18 mm., breadth ·11 mm.; the side walls of the area bear about a dozen tubercles so small that their existence is only just recognizable under a 3 in. objective; a 1 in. objective shows them to be perforated; below the area there is typically (after the early stages) a small perforated boss placed centrally on the front wall, but when the front wall has to accommodate an oœcium the boss splits into two, often very massive, one on either side of the oœcium.