The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Valve clavate, with capitate or rostrate-capitate apex and narrow basis; axial area very narrow; central area small, unilateral, with one stigma.

Common in fresh water.

Pl. [19], Figs. 9 and 10. Fig. 10 appears to be a transitional form having a more distinct axial area and rostrate apex.

GOMPHONEMA AUGUR EHR.

Valve broadly clavate, truncate and apiculate at the apex; basis sub-acute; axial area distinct; central area small, unilateral with one stigma; striæ with distant puncta.

Blue clay. Willistown, Pa.

Pl. [19], Fig. 21.

GOMPHONEMA INTRICATUM KUETZ.

Valve narrow, lanceolate, slightly gibbous in the middle; axial area distinct; central area transverse with one stigma; striæ parallel. Quite variable.

Common in fresh water.