The Diatomaceæ of Philadelphia and Vicinity

The study is of advantage in relation to the life history of aquatic animals, the determination of ocean currents, as proved by polar discoveries, the investigation of geologica...

It may be assumed that diatoms originated in the sea; to deny this requires evidence of the existence of fresh-water species previous to the Miocene period which is entirely mar...

Margin striated, the alternate striæ thickened near the border, producing an appearance of subquadrate cells. Centre faintly granulate, the outer border of which is encircled by...

Valve elliptical or subcircular, median areas distinct, rounded, circumscribed by coarse distant costæ radiating near the border where they are more evident, and converging towa...

Valve ovate, attenuated to the rounded inferior apex; pseudoraphe indistinct, striæ fine, 24 in 10 µ. Zone view broad, cuneate, angles rounded, inferior apex broad; frustule rob...

Very many species of Eunotia have been created to differentiate size and number of crenæ or undulations. An examination of certain fossil deposits of New England, as well as a g...

Valve about three times as long as broad, strongly convex on the dorsal side and straight on the ventral; apices sub-rostrate; striæ punctate; axial area narrow, not widened in...

Valve slightly biconstricted, with obtuse apex and basis, somewhat cuneate; axial area linear, widened in the middle unilaterally; stigma, one; striæ about 11 in 10 µ, more dist...

I have retained Lewis' name as specific. Lewis, wrongly, I think, ascribes his species to _Navicula trinodis_ Wm. Sm., which is not figured by Smith, but is illustrated by Van H...

Cleve gives the striæ as 13-18 in the typical form, and 11-13 in varieties. In the form here figured the striation is as stated by De Toni, but is about 19 at the ends.

The costæ are channels on the inside of the valve, closed, except in the middle where elliptical foramina, opening into the interior of the valve, give rise through their termin...

Frustule elliptical, slightly constricted in the middle. Valve convex on the dorsal, straight on the ventral side; costæ about 4 in 10 µ; striæ about 18 in 10 µ, finely punctate...

The type form occurs in brackish and salt water. The occurrence of the variety in fresh water is another instance of the finding of presumably brackish forms in the water supply...

_Preparation of Strewn Mounts._--Place several covers on the mounting stand. With a dipping tube, cover each circle with distilled water, and add a small drop of the prepared di...

Gomphonema, 70 acuminatum, 71 var. coronata (Ehr.) Cl., 71 var. trigonocephala (Ehr.) Cl., 71 var. turris (Ehr.) Cl., 71 var. turris (Ehr.) Cl.?, 71 æquale Greg., 72 angustatum...

Synedra, 47 acus Kuetz., 48 affinis Kuetz., 50 var. parva (Kuetz.) V. H., 50 var. tabulata (Ag.) V. H., 50 biceps (Kuetz.) A. S., 48 capitata Ehr., 48 danica Kuetz., 48 fulgens...