44 COCCOPHYCEZ. 
or almost obsolete; cells of the disc perforated ‘with smaller 
openings. 
Pediastrum tricyclum, Hassall Alg. t. 92, f. 1. 
Pediastrum Napoleonis, Hassall Alg. t. 92, f. 10. (?) 
Plate XVII. fig. 6. a, 5-celled coenobium; 4, 16-celled coenobium, fig. 
4; f, marginal cell. 
Section 4. rverractinitm. Braun. 
Cells of periphery emarginate or bilobate; lobes emargi- 
nate, bidentate, or bifid. 
Pediastrum Ehrenbergii, Br. Rabh. Alg. 111., 72. 
Ceenobium orbicular or oblong, perfectly closed, composed of 
8-16 cells, or quadrate, of 4 cells, which are wedge-shaped, 
deeply lobed and arranged in the form of a cross; cells of the 
periphery cuneate, truncate at the base, deeply bilobate; sinus 
narrow, lobes obliquely truncate, more or less notched, interior 
angles twice as long, all acute, or shortly appendiculate ; central 
cells yellow green, polygonal, one side repand or deeply notched. 
Pritch. Infus. t. 1, f. 52. 
Pediastrum tetras, Ralfs Desm. t. 31, f. 1. Ralfs Ann. Nat. 
Hist. xiv. (1844) t. 12, f.4. Hassall Alg. t. 86, f. 17. 
Pediastrum heptactis, Ralfs Ann, Nat. Hist. xiv. (1844) t. 
12, £5. Ralfs Desm. t. 31, f. 2. 6, 4.16 
Pediastrum simplex, Hassall Alg. t/ 84-47. 
Pediastrum biradiatum, Ralfs Desm. t. 31, f. 3, 4. 
In pools and boggy places. Not uncommon. 
Very variable in size. The 4-celled ccenobia are often to be met 
with, mixed with Desmids and other Alge. 
Plate XVII. fig. 1. a, four-celled cconobia; 8, 8-celled ccenobia; ¢, 
8-celled coonobium of unusual form, after Ralfs. 
var, a, truncatum. Braun Unicell. Alg. p. 97. 
Lobes truncate. 
Pediastrum biradiatum, Ralfs Desm. t. 31, f. 4. 
Plate XVIII. fig. 1. 0b, 8-celled czenobia. 
var. b,.excisum. Braun Unicell. Alg. p. 97. 
Lobes slightly notched, emarginate. 
Plate XVIII. fig. 1. d, 4-celled coenobium; e, 8-celled ceenobium; 
4, k, 16-celled ccenobia. 
var.c. cuspidatum. Braun Unicell. Alg. p. 97. 
Lobes deeply notched, evidently bidentate or bicuspidate. 
Pediastrum biradiatum, Ralfs Desm. t. 31, f. 3. 
In stagnant water, throughout Europe generally. 
Plate XVIII. fig.1. 9, h, coenobia; f, marginal cell. 
