BIDDULPHIOIDEÆ
BIDDULPHIEÆ
(a) Triceratiinæ.—Frustule cylindrical or prismatic, with three or more sides.
(b) Biddulphiinæ.—Frustule cylindroid; valve with ends elevated into round processes or long horns.
(c) Anauleæ.—Valve elliptical, lunate or triangular, with internal septa.
(d) Euodieæ.—Frustule cuneate in zone view; valve lunate.
(a) TRICERATIINÆ
(1) Ditylum.—Frustule imperfectly siliceous. Zone with numerous divisions. Valve with central spine.
(2) Trinacria.—Processes with sharp spines.