134 SKETCH OF THE INFUSORIA 



8. Closteriwn tenue, Ktz. " Corpnsculis minutis lineari-lanceolatis, 

 viridi hyalinis, transverse fasciatis, acutis." See Liniitca, 1833, PI. 8, 

 fig. 78. 



I find no notice of this species in the extract from Ehrenberg's 

 work, appended to Mandl's work on the microscope, but as Kut- 

 zing's fig. 78 resembles our species, (fig. 37, PI. I,) 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 ^uch 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 cara- 

 pace, and it often appears as if a portion of the shell between 

 these lines (as at o, b, fig. 37, pi. I,) had been removed. Its 

 motions are distinct and lively. 



9. Closterium . (Fig. 38, PL I] Nearly cylindrical, con- 

 tracted 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, PL I.) 



MICROTHECA. 



Free, carapace simple, univalve, compressed, separate, lamelli- 

 form. 



M. octoccros. Carapace quadrangular, hyaline, four spines at each 

 end, internal body golden yellow. 



I am unacquainted with this genus. 



NAVICULACEA. 



Having given in the preceding part of this memoir, some ac- 

 count of those Bacillariae which belong to the section Desmidi- 

 acea, I continue the subject, by describing the Bacillai-ias of the 

 section Naviculacea. 



As all the species referred to this section have siliceous cover- 

 ings, 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 beings. 



