Читать книгу The Diatomaceæ of Philadelphia and Vicinity - Charles S. Boyer - Страница 28

Valve circular, usually divided into fourteen sectors which are on the same plane at the centre, but the alternate ones are elevated into mammillated projections terminated by small processes on the margin. Zone view rectangular with undulations subconical, terminated by the processes.

POLYMYXUS CORONALIS L. W. BAIL.

Central space hyaline, rounded or slightly stellate, from which radiate rows of fine puncta in quincunx, shown in the figure only on the alternate elevations, the depressed interspaces being out of focus. The mammillæ are stated by Bailey to vary from six to ten.

Very rare in the blue clay (Walnut St. Bridge). Occurs also in the Wildwood deposit (Bull. Torrey Bot. Club, 1895, p. 261).

Pl. 4, Fig. 7, and Pl. 5, Fig. 2.