XXVl1 
DESCRIPTION OF PLATE IV.—continued. 
Fig. 16.—Eunotia turgida: 3, of a line; the empty shell, with sixty-five ribs, 
viewed laterally. 
17.—A living group of the same: 3, of a line: a piece of Conferva rivu- 
laris, beset with these animalcules. The smaller species are E. Wes- 
termanni. 
[All the above organisms were figured and described by Ehrenberg as animals 
(Polygastrica), and are comprised in his family Bacillaria; they are now, how- 
ever, regarded as unquestionably vegetable structures, belonging to the family 
of ALG#, termed Diatomacee. | 
