18 
Wood 
margin ; semicells broadly elliptical, with a single straight or diverg- 
ing aculeus at each end. Diameter of cell, without aculei, 38// ; 
with aculei, 6^pi. 
This plant was gathered with Sp/iag mi m (bog-moss) by Mr. E. A. 
Rau in a pond near Newfield, N. J., in the month of August last. 
It bears some resemblance to A. divei-gens, Rab., but it is not 
"subtilissime verruculosus ;" also to A. quadridens, 
twice the size of that plant, and is not quadridens. 
A. OVALTS, n. sp. — Cell small, smooth, about one-fourth longer 
than wide ; semicells oval, armed at each end with a straight or 
divergent aculeus. Diameter, without aculei, 20//. 
Ponds, Mount Everett, Mass. 
A. Incus, Breb., comes near this form in size, but is unlike it in 
its truncate ends. 
A._ ORBICULARIS, n. sp. (Plate xxvii., Figs. 22 and 22^;, front and 
end views).— Cells very small, smooth, orbicular ; semicells united 
by a narrow isthmus ; aculei on opposite sides nearly parallel. Dia- 
meter, without aculei, 12//. 
Pond, Mount Everett, Mass. 
EUASTRUM, Ehrb. — E. mammillosum,«. sp. (Plate xxvii., Fig. 
21).— Cell large, in length twice the diameter ; semicells three-lobed ; 
basal lobes wide and nearly half as high as the semicell, drawn out 
in the centre into a narrow column about one-fourth the width of 
the body, dilated at the end, sinuate, four-parted; base with six 
mammiform protuberances ; membrane punctate ; end view oval, 
with three diverging mammiform, prominences at each end. Dia- 
meter of centre of cell, 68//; of the ends, 28/* ; length, ii8;/. 
Pond, Mount Everett, Mass. 
A distinct species ; the protuberances a prominent feature, 
E. cuspiDATUM, n. sp. (Plate xxvii., Fig. 18).— Small ; diame- 
ter shghtly less than the length; semicells distinctly three- 
lobed, basal lobes extending laterally their own width ; end lobe 
subrectangular, twice the width of the other lobes, obtusely sinuate 
in the centre ; ends of the rounded basal lobes, and of the two sec- 
tions of the end lobe, surmounted each with three firm, diverging 
aculei. Diameter of cell, without aculei, 25// ; length, t,^^. 
Pond, Absecom, N. J. Contributed by H. D. Kitchel. 
E. binale, var. majus, n. var.—ln all its details, except size like 
the typical form, the dimensions being double the ordinary measure- 
ment. Diameter, 40// ; length, 55//. 
In a pond near Newfield, N. J. Collected by E. A. Rau. 
E. inerme, Lund., var. depressum, n. mr.— The standard form is 
nearly twice as long as wide, but the present form is only one-third 
longer than wide, and this difference produces a depressed appear- 
ance. Diameter, 36yu-4o>u; length, 5o/<-55//. 
Newfield, N. J. Collected by E. A. Rau. 
MICRASTERIAS, Ag.— vl/. brachyptera, Lund., var. Americana 
«. var. (Plate xxvii.. Fig. 19).— Distinguished from the form found 
m Sweden and described by Lundell, the polar lobe not being 
inwardly distended, but more or less tapering. The curved points 
on the apices of the lateral lobules are usually in jiairs, not in threes 
