INFUSORIA. 
75 
Bacillaria paraioxa. (PL 22, %. 35.) The standard beao-er. Striate, carapace linear, very slender, 
often fifteen times longer than broad, yellow, frustules very active, Jg- to Jg line. Syn. Vibrio 
paxiltifer, Mueller. (See Encyl. Meth. PI. 3, fig. 16 to 20.) 
I first detected this species in October, 1840, among algae from the Hudson river, near West- 
Point. I am informed by Dr. P. B. Goddard of Philadelphia, that it also occurs in abundance 
' near that city. It is a very interesting species, presenting by its curious motions and para¬ 
doxical appearance an object well calculated to astonish all who behold it. At one moment, 
the needle-shaped frustules lie side by side, forming a rectangular plate ; suddenly, one of 
the frustules slides forwards a little ways, the next slides a little also, and so on through the 
whole number, each however retaining a contact through part of its length with the adjoining 
ones. By this united motion the parallelogram is changed into a long line ; then some of the 
frustules slide together again, so that the form is then much like a standard. Similar motions 
are constantly going on, and with such rapidity that the eye can scarcely follow them. There 
are few more interesting objects for the microscope. 
Several of the positions of these singular productions are well represented by Muller. 
(See Enc. Meth. Vers. PI. fig. 16-20.) Muller found his specimens abundant on Ulva latis- 
sima ; I found mine pretty common among Enteromorpha, Polysiphonia, Potamogeton, which 
grow together in brackish water on the flats in the Hudson river, near West-Point. 
Bacillaria? tabellaris. (PI. 22, fig. 36, a, b.) Smooth, carapace linear, narrow,, swollen in the 
middle, dividing into quadrangular plates of variable length, ovary lobed and yellow, to 
line (width of filament.) Syn. Diatoma flocculosum, Kuetz. (Linn. 1833, PI. 17, fig. 67.) Dia- 
toma flocculosum, Greville, in Brit. Flora, Vol. Y. p. 406. 
This species is very common in all parts of the United States which I have visited. It is 
easily recognized by its zigzag chains, composed of plates (individuals) of various width, 
which have the middle and two outer edges considerably thickened,' as is shown in the side 
view, fig. 36, b. 
In fig. 37, a, b, is represented what I believe to be the full grown state of the species. It 
at first view appears very distinct from fig. 36 ; but on examination, we find the same thick¬ 
ening of the middle and ends, and similar transverse lines. The two varieties or states occur 
together ; both are also found fossil. They are very abundant in ditches and ponds near 
West-Point. 
Bacillaria -. (PI. 22, fig. 38.) This is a marine species, which I found at Stonington, Conn. 
and Staten Island, N. Y., adhering to filamentous algas. It is distinguished by having on each half 
of its frustules two lines which commence near the centre, and run straight and parallel until they 
arrive near the extremities, when they suddenly become falcate for a short distance, and then resume 
their original directions. The curved portions of the lines have some resemblance to the upper por¬ 
tion of a pair of tongs. The position of these lines is very similar to those on Bacillaria mene- 
ghinii. (See Schlechtendal’s Linnsea, 1840, Tab. IV. fig. 1.) 
Tessella. Free ; carapace simple, bivalve or multiviilve [siliceous), prismatic, compressed in form 
of plates; forming zigzag polypidoms by imperfect spontaneous division of the body, and per¬ 
fect division of the carapace. The chains have spontaneous motion. 
