292 Sketch of the Infusoria of the family Bacillaria. 
I must here remark that a transition from Xanthidium to Eu- 
astrum appears quite evident, through the binary triangular bod- 
ies, wep ve projecting arms, represented in figures 2, 3, 4, 9 
and 
ARTHRODESMUS. 
Free, carapace simple, univalve, compressed in the form of @ 
te or a compressed band, articulated by spontaneous division. 
. Arthrodesmus quadricaudatus. (Fig. 17, Pl. 1.) Corpuscles ob- 
he straight ; chain or polypidom of four to eight individuals formed 
by mes et spontaneous division, four horns, (the middle corpuscles 
rounded at the ends, the others with a horn at each end.) ‘Size of cor- 
puscles +45 to si; line ; chains 4/5 line. Scenedesmus magnus, Meyen. 
This species, as it occurs in this country, is composed of from 
four to eight green elliptical corpuscles arranged in a thread or 
chain, usually having horns only on the two extreme corpuscles, 
but not unfrequently similar projections may be seen on the mid- 
dle ones also. Meyen, who considers this as a plant, states that 
in spring it contains starch globules. * Tt is extensively diffused, 
both in Europe and in this country ; I have noticed it as far west 
as Ouisconsin, and south to Virginia. It is abundant in ponds 
hear West Point, fi € 
2. Prarie Bias cutus. (Fig. 18, a, b, Pl. 1.) Corpuscles green, 
oblong, alternating in a right line, by spontaneous division. 
The small green bodies represented in our fig. 18, occur in the 
well at Fort Putnam, —_ Point. They appear to belong to 
- species. 
OponTeLLa. 
” Pree, carapace simple, univalve, compressed, form of flattened 
articulated ribbands, often pierced, produced by imperfect sponla- 
neous division, articulations united by small projections. 
I have. not satisfactorily determined any American peat of 
this genus, although I have occasionally seen small_filame 
which agreed tolerably well with the generic character. 
ee iptintaitse. 
a ce simple, univalve, compressed, groups of a num 
pa individals is frm of a atone star, produced by sal 
cous di 
Fen, Pftanzen Paani Vol. 3, past. 
