PEDIASTRUM. 389 



3. PEDIASTRUM ELEGANS Hass. 

 Plate LXXXVI. Fig. 19. 



Char. Frond circular, star-like, composed of six marginal 

 crescentic cells, and two central cells of an angular form. 



Pediastrum Napoleonis Ralfs, in Annals, vol. xiv. p. 470. 



pi. xii. fig. 6. 

 Hal. Dolgelly : Mr. Ralfs. 



The above species, described and figured by Mr. Ralfs 

 under the name of Pediastrum Napoleonis, and as the Micra- 

 sterias Napoleonis of Ehrenberg bears no resemblance what- 

 ever to the figures given of that species, nor indeed to any 

 of Ehrenberg's figures, save a distant one to fig. 5 e. of pi. xi., 

 which is regarded by the author as a state of Micrasterias 

 Boryanum, which it certainly cannot be, as the frond in the 

 figure alluded to is made of ten marginal crescentic cells, and 

 five internal angular cells. 



4. PEDIASTRUM BORYANUM Menegh. 

 Plate LXXXVI. Fig. 13. 



Char. Frond composed usually of two circles of cells, en- 

 closing a central cell, but sometimes there are three and 

 even four concentric circles, inner circle formed of Jive 

 cells, and second circle of ten. Marginal cells deeply bifid. 



Helierella Boryana Turpin, Mem. du Mus. vol. xvi. p. 319. 

 pi. xiii. fig. 22. 1828. Pediastrum simplex, P. duplex, 

 P. biscidiatum Meyen, Nov. Act. Nat. Cur. xiv. 1829, p, 

 772, 773. t. 3. figs. 7. 13, 14. 16, 17, 18. ; Isis, 1830, 

 p. 163. Opharium speciosum, O.formosissimum, et O. ver- 

 ticillatum Losano, Mem. de Zarino, xxxiii. 1829 ; Isis, 

 1832, p. 768. t. xiv. figs. 17, 18. 21. Micrasterias sim- 

 plex, M. Boryi, M. duplex, et M. Selancea Kiitzing, Lin- 

 naea, 1833, p. 601. 3. t. xix. fig. 92 b. Euastrum 

 pentangulare et Pediastrum quadrangum Corda, Almanac 

 de Carlsbad, 1835, p. 206. 7. t. iii. figs. 32. 35. Mi- 

 ce 3 



