The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

This has the outline and appearance of S. oblonga Ehr. (Mik. Pl. 15, Fig. 48), but the costæ are closer.

SURIRELLA RECEDENS A. S.

Valve ovate; costæ, 2-2½ in 10 µ; pseudoraphe narrow, not reaching the ends of the valve; intercostal spaces more evident near the middle. L. 50 µ.

Blue clay. Not uncommon.

Pl. [35], Fig. 7.

SURIRELLA CRUCIATA A. S.

Valve ovate; pseudoraphe very narrow; costæ, 2 in 10 µ; the outline of several of the median costæ strongly emphasized, while the other costæ are indistinct. L. 54 µ.

Blue clay.

Pl. [35], Fig. 10.

SURIRELLA GRACILIS GRUN.