304 Sketch of the Infusoria of the family Bacillaria. 
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, Pl. 1.) 
Microraeca. 
Nig carapace simple, univalve, compressed, separate, lamelli- 
M octoceros. Carapace quadrangular, hyaline, four spines at each 
end, internal body golden yellow. 
am unacquainted with this genus. 
End of the Desmidiacea, 
Note. —Having, i in what precedes, completed a sketch of the Desmi- 
diacea, I propose to offer in the next part of this memoir (now nearly 
ready for the press) some account of the other divisions of the Bacilla- 
ria, viz. the Naviculacea, the Echinellea 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 Prof. W. B. Rogers, of the vast infusorial stra- 
tum in the tertiary of Virginia,* cannot fail ® attract new attention to 
tibs6 interesting bodies. 
anation of the Figures, on Plate I. “he sketches which accom- 
pany this memoir, were all made by means of a camera lucida ye 
piece attached to Chevalier’s ‘horizontal and vertical microscope. 
fig. 39 is shown a sketch of +19,ths of a millimetre, magnified and drawn 
with the same combination of lenses, camera lucida, distance, &c. This 
being equally magnified with the drawings, will serve as a scale to de 
termine the absolute dimensions of any of the objects. The highest 
power of the instrument was not used in getting the outlines, as it would 
have given figures inconveniently large. The details were, however, 
oceasionally corrected or confirmed, by the use of a higher power. — 
: PLATE I 
Fig. 1. Desmidium Schwartzii, Page 288, from a twisted portion of a 
filament. 
Fig. 2 and 3. ‘Bumtrum} page 296, two positions of same individual. 
Fig. 4 and 5. Euastrum? a larget variety of the same species as fig. 3. 
Pig. 5. Se ee ree ere a betes in a state 
Fig. 6. Sasi tiga. 
Fig. 7. Frearaed aay of 4, page 296, tig 
AL IE 
ae sel of this Journal, Pp 214. . 
* dead pots of this tis means eos ae 
