Sketch of the Infusoria-of the family Bacillaria. 295 
4. Euastrum (Fig. 25, Pl. 1.) This very elegant form is 
somewhat rare. It occurs at West Point with the preceding. 
5. Euastrum (Fig. 26 and fig. 27, a, b, c, and d, Pl. 1.) I 
suspect that the species represented in figs. 26 and 27, is the same as 
the Echinella oblonga of Greville, which he describes as being “ com- 
pressed, oblong crenato-pinnatifid, and lobed, divided transversely al- 
most to the centre.” (Brit. Flora, Vol. V, p. 398.) 
Fig. 27, a and b, show two positions of the same individual: 
eand d show aiatt individuals, which are probably the young of 
this species. Fig. 26, although much more deeply lobed than 
fig. 27, is probably only an older state of the same. They oceur 
at West Point, also near Detroit, Michigan, and in Ouisconsin. 
6. Euastrum (Fig. 28, a, b.) This species is neither lobed 
hor undulate ; but while the general outline is convex, a minutely ser- 
rated edge may be seen. When thrown on its side, (fig. 27, b,) it pre- 
sents an unusual thickness. 
If this species is compared with fig. 38, Pl. 1, the close rela- 
tion existing between the Sener Closterium and Evuastrum will 
be manifest. 
7. Euastrum ~ (Fig. 29, PL 1) T suspect that the bodies 
represented i in fig. 29, hong to ‘fis genus. They consist usually of 
four somewhat elliptical green bodies placed parallel to each other, and 
united laterally, as seen in the figure. Each elliptical portion is biden- 
tate at the ends. I have met with specimens in which eight such cor- 
puscles were united, producing such an appearance as would be given 
if a figure like that shown in fig. 29, had a similar one added immedi- 
ately below it. 
If this is a species of Euastrum, perhaps it may be thus char- 
acterized ; Euastrum ———. Fig. 29. Binary (or sometimes 
ghaternary,) each corpuscle divided by deep lateral sinuses into 
two transverse somewhat elliptical bidentate portions, the middle 
portions longest. Occurs in ponds near West Point. 
8. Euastrum margaritiferum, Ehr. (Fig. 8, a, 6, Pl. 1.) Body. bi- 
hary, elliptical, each part semi-orbicular with the margin entire, 75 to 
zz line. Heterocarpella tetropthalma, Ktz. Linn. 1839, Pl. 19, fig. 87. 
. Our species (fig. 8) agrees pretty well with the above descrip- 
tion and with Kutzing’s figure. A figure given by Meyen in his 
Pflanzen Physiologie, Vol. III, Pl. 10, fig. 31, apparently belongs 
to this species also, 
‘The surface has a great number of minute hemispherical pro- 
jections, disposed in a quincuncial order. It is possible that the 
