322 Sketch of the Infusoria of the family Bacillaria. 
tests. A good idea of the general form of this genus may be got 
from Plate 4, fig. 153, of Pritchard’s Infusoria. 
SYNEDRA. 
Carapace simple, siliceous, fied when young by one extremity, 
when older often free, longer than broad, foot either wanting or 
rudimentary, form elongated or prismatic. 
Synedra > (PI-3, fig. 1.)* Frustules long, slender, linear, 
adhering laterally into plates which are supported by a short fleshy 
pedicel, and terminated by a fleshy mass. 
The species whose usual appearance is shown in PI. 3, fig. 1, 
occurs in vast quantities on various Alg in the Hudson River at 
West Point. It usually completely envelopes the plants to which 
it is attached, giving them a covering of bristling erystal-like par- 
ticles, through which it is often difficult to see any portion of the 
supporting plant. When the Algz on which it grows are dried, 
they often have a greenish gray hue, from the presence of this 
asite. 
It presents considerable resemblance to S. Gailloni, Ehr. (Dia- 
toma crystallinum, Ag.) and has, like that, minute striae on the 
edges, but I have seen no allusion made in the descriptions of 
that species to the fleshy projection which is so conspicuous in 
our species. ; 
A person who sees how abundant this species is in the recent 
state, will no longer wonder that in the lapse of years masses 
of infusorial shells should accumulate so as to form extensive 
Synedra >? (PL. 3, fig. 2.) Frustules linear, strait, striate; 
truncate on the lateral side, ventral sides with a neck-like contraction 
near each end, ends rounded. 
This species is very abundant in fresh water near West Point, 
often covering aquatic plants with a glittering envelope of cry stal- 
like frustules. ‘The individuals are perfectly linear with truncate 
ends. When seen laterally, they show near their extremities 4 
slight contraction, which forms a neck supporting the round or 
knob-like terminations. Minute strie may be seen as present 
hich accompanies this part of Prof. Bailey’s article, 7 also eee 
tes contained in the present volume of ‘this Journal. pee 
A an | plate ate V at the top of ‘the plate.—Eps. ey 
