Sketch of the Infusoria of the family Bacillaria. 293 
This is a very beautiful genus, its species presenting elegant 
star-like arrangements of green corpuscles, some of which closely 
resemble in form the stars and badges of honor worn in Europe. 
There appears to me to be much confusion in the specific char- 
acters, arising from the circumstance, that the nwmber of corpus- 
cles in the different rows has been made a character of specific 
importance. From what I have seen of the species, 1 am satis- 
fied that the number of corpuscles in a star is liable to great va- 
tiation in the same species, Perhaps the form of the corpuscles 
would prove a more certain character. 
1. Micrasterias Tetras. (Fig. 19, Pl.1.) Four corpuscles united 
in form of star, the edge slightly notched. 
This is a very minute species, which occurs in ponds near West 
Point. I have also noticed it in Virginia. 
2. Micrasterias Boryana... (Fig. 20, Pl. 1.) Ten corpuscles in the 
exterior circle, five in the ais and one in the centre, edge acutely 
dentate, Corpuscles ,!; to +35 of line. 
_ dt happens accidentally that our figure represents an individual 
having just the number of corpuscles above described. I am 
satisfied, however, from frequent observation, that the same spe- 
cies sometimes has a much greater number of corpuscles, certainly’ 
another row of fifteen is often developed. It then agrees with 
M. tricyclia of Ehrenberg. It is a very beautiful object for the 
microscope. I have found it in New York, Virginia, and in Quis- 
consin. 
3 Micrasterias (Fig. 21, PL. 1, ) Corpuscles very nume- 
rous, forming large imperforate plates of a circular or elliptical form, 
Exterior corpuscles soe emarginate, each having two projecting 
Points, 
This large and very beautiful species is not uncommon in ponds 
near West Point. 
Evastaun. 
| Free, carapace simple, univalve, compressed, binary, sometimes 
~cinelaoed having the form of a two-lobed disc or lamina, often 
“The elegant forms and emerald green color of the species of 
genus render them exceedingly fine. objects for the micro- 
Scope. The forms, as usually seen, appear tabular, but when 
thrown on their sides b yt means of Kemiae they show con- 
siderable thickness. 
