Valve cylindrical, with a crown of stout spines less than the diameter of the valve near the margin. Cells hexagonal, about 2 in 10 µ, sometimes punctate. The valve having the greater convexity has the larger spines, though usually less of them.
Creswellia turris Grev. (Gregory, Diat. of the Clyde, T. R. S. E., vol. 21, part 4, p. 66.)
Stephanopyxis appendiculata Ehr.?
Creswellia is incorrectly based, as stated by Ralfs, on the concatenation of the valves which was not noticed by Ehrenberg in the fossil forms. It had been suggested by Kuetzing in Systema Algarum (p. 126).
Blue clay. Port Penn and Smith's Island.
Pl. [2], Figs. 1 and 2.
STEPHANOPYXIS CORONA (EHR.) GRUN.
Valve larger than in turris, sub-globose, coarsely areolate cells, 4-5 in 10 µ. One valve furnished with a crown of teeth shaped like the letter T and united at the top into a ring above the margin of the valve; the other valve with long spines more or less concentrically arranged.
Blue clay. Not common. Fossil in the Nottingham deposit.
Pl. [2], Fig. 3.