Frustules single or in twos, usually broader than long, constricted near the margin. Valve with six to twelve internal projections forming with the outline of the constriction of the valve a polygonal figure within the circumference. Surface of the valve with radiating lines of puncta disappearing toward the centre, at which are numerous coarse puncta.
Meloseira gowenii A. Schmidt.
Blue clay of Philadelphia, especially common at Twelfth and Market Sts.
Pl. [1], Figs. 15, 16, 17.
MELOSEIRA SULCATA KUETZ.
Frustules quite robust, with diam. several times the length, deeply furrowed at the margin, areolate and punctate. Valve with radiating striæ disappearing toward the centre, and with a double row of cells near the margin, the outer one having the appearance of a crown of teeth.
Gaillonella sulcata Ehr.
Paralia sulcata (Ehr.) Cleve.
Paralia marina Heib.
Marine and brackish. Common in all parts of the world, and fossil in the Miocene. The Philadelphia form is the var. genuina Grun.