19 
4 
The arrangement of the aculei on the membrane of the cell is also 
distinct. The size is very nearly the same, the width being 150/^ 
and the length 190//. 
Collected in a pond near Minneapolis, Minn. 
M. conferta 
./ 
lobes, as in the original form, but widely separated in the middle 
by a deep notch or contraction below the apex, thus giving the lobe 
a hamate form. Diameter, 88/^-100//, slightly longer than wide. 
Ponds, Mount Everett, Mass. 
M. PSEUDOTORREYT, ;^. sp. (Plate XXVII., Fig, 2). — Large, circular, 
five-Iobed ; basal and intermediate lobes bisected, sections more or 
less conical, ends truncate and deeply furcate ; polar lobe broadly 
cuneate, end truncate, slightly sinuate, angles cuspidate. Diameter 
of cell, iSoyU. 
M 
M. 
less number of lobules, and their greater similarity of form. 
M. pseudofurcata^^NoW^^ var. minor, n. var. (Plate xxvii., Fig. 4). 
Only half the size of the typical form, and in structure firmer. Dia- 
meter, 63/^-75/^. 
Minneapolis, Minn. 
^STAURASTRUM, Mey.— 5/. striolatum, Nteg., and St.pygmceum, 
Breb., var. obtusum^ Wille, in quiet waters, Pennsylvania. St. spiiiosinn^ 
Brcb., and St. aculeatum^ Ehrb., both from Minneapolis, Minn. 
St. paniculosum, n, sp, (Plate xxvii., Figs. 3 and 3a, front and 
end views.) — Cell sexangular, as long as wide ; semicells truncated 
triangles, angles rounded ; inferior angles bearing two short, straight 
aculei ; end view triangular, one aculeus visible on each rounded 
angle; sides moderately convex; membrane punctate, punctules in 
radiating lines. Diameter, 40/^-50//. 
Marsh pool near Bethlehem, Pa. 
St. duplex, n, sp, (Plate xxvii., Figs. 10 and 10^),— Of equal 
length and breadth, subquadrangular.; constriction deep, enlarged 
outwardly ; angles rounded, furnished with two short, stout pro- 
cesses, ends truncate, granulate or spinous ; end view triangular, 
sides straight or concave, angles divided and drawn out into two 
short, somewhat divergent processes, ends furnished with three €)r 
four very small teeth. Diameter, 20//-25//. 
Pools on shore of river, Bethlehem, Pa. 
The end view has a resemblance to Nordstedt's St. gemelliparum^ 
but the front view is distinct. 
St. exiguum, 7t, sp, (Plate xxvn.,'Figs. 23, 23^ and 23^.)— Very 
small, smooth or punctate ; semicells subcuneate, sides slightly 
rounded, ends truncate ; superior angle produced into straight, 
divergent arms nearly as long as the diameter of the cell ; ends 
forked ; viewed from the end, triradiate. Diameter, including 
arms, 20/^-25/i. 
Frequent in ponds, Mount Everett, Mass. 
This minute form is nearest St. gracile, Ralfs, but differs in its 
smaller size and smoother membrane. 
