INFUSORIA. 65 
work on the microscope; but as Kiitzing’s fig, 78 resembles our species, (Fig. 37, PI. 21,) 
I quote his description, that they may be compared. 
Our species occurs in vast abundance on the muddy bottom of a brook which crosses the 
Canterbury road, a few miles from West-Point. It forms a mass of such extent, and of so 
bright a green color, that I at first mistook it for a layer of Oscillatoria. 
There are very fine transverse lines, often visible on the carapace, and it often appears as 
if a portion of the shell between these lines (as at a, h, Fig. 37, PI. 21) had been removed. 
Its motions are distinct and lively. 
Closterinm -. (Fig. 38, PI. 21.) Nearly cylindrical, contracted in the middle, ends obtuse, and 
in one position showing a re-entering fold of the carapace. Hab. ponds near West-Point. A similar 
fold in the carapace is visible in some species of Euastrum. (See Fig. 27, PI. 21.) 
Microtheca. Free, caraface simple, univalve, compressed, separate, lamelliform. 
Microtheca octoceros. Carapace quadrangular, hyaline, four spines at each end, internal body golden 
yellow. 
I am unacquainted with this genus. 
Note. Having, in what precedes, completed a sketch of Desmidiacea, I propose to offer 
next some account of the other divisions of the Bacillaria, viz. the Naviculacea, the EcM- 
nellea and the Lacernata. Many of the species of these families have siliceous coverings, 
and are found in a fossil state. An account of our American species will, therefore, I trust, 
be found of some interest to American geologists, especially as the recent discovery by W. 
B. Rogers, of the vast infusorial stratum in the tertiary of Virginia,* * * § cannot fail to attract 
new attention to these interesting bodies.! 
Section II. NAVICULACEA! 
As all the species referred to this section have siliceous coverings, they often occur in a 
fossil state, and hence their study is of peculiar interest to the geologist. In beauty of form 
and elegance of structure, they will bear comparison with almost any class of organized be- 
ings.§ 
* See a notice of this discoveiy in the American Journal of Science, Vol. 31, p. 214. 
+ Since the preceding sketch was sent to press, I have seen in Schlechtendal’s Linnma for 1840, p. 201, a valuable memoir, by 
J. Meneghini, entitled Synopsis Desmidiarum hujusque cognitarum. It gives a very good account of the genera and species, with 
copious lists of synonims. I find my views as to the relations of several genera confirmed on perusal of this Synopsis, which I 
recommend to the attention of students of this curious class of bodies. J. W. B. 
t These are all siliceous, and therefore often occur abundantly as fossils in peat bogs, and also in the silt and mud of rivers, 
ponds and marshes. J. W. B. 
§ Since the second part of this article was ready for the press, I have received Pritchard’s beautiful work entitled “ History of 
Infusoria, living and fossil.” I have gladly availed myself of the opportunity to introduce here many of the novel facts which it 
contains. Many of these facts will be given in the form of notes, as time does not now allow me to incorporate them in this 
sketch in any other form. J. W. B. 
Geol. 1st Dist. 
9 
