The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Along the coast.

Pl. [15], Figs. 9 and 10.

AMPHORA OSTREARIA BRÉB.

Frustule oblong, with rounded angles. Zone with five or more divisions transversely striated. Central area narrow, biarcuate; central nodule dilated to a stauros. Valve narrow, with arcuate dorsal and straight ventral margin, acute at the ends. Striæ transverse, finely punctate.

A. vitræa Cl.; A. porcellus Kitton; A. quadrata Bréb.; A. elegans Greg. Appearance varies according to the position of the valve.

Along the coast.

Pl. [15], Figs. 12 and 21.

AMPHORA LÆVIS GREG.

Frustule oblong, hyaline and membranaceous. Valve linear or slightly arcuate, with ventral margin tumid in the middle; ends obtuse; central nodule dilated to a stauros; median line very narrow, biarcuate, coinciding with the dorsal margin at the ends; striæ transverse, punctate.

Blue clay.