394 DE8M1DEJE. 



equally ventricose, arranged in a double, irregularly alter- 

 nating series." 



Arthrodesmus acutus Ehr., Infus. p. 150. tab. 10. fig. 19. 

 c, d ; Meneg. 1. c. p. 207. ; Ktitz. 1. c. p. 609. fig. 96. ; 

 Ralfs, in Annals, vol. xv. p. 403. pi. xii. fig. 6. 



" I notice this species because the Rev. M. J. Berkeley 

 has gathered it near King's Cliff, and I have occasionally 

 met with specimens which agree with Ehrenberg'e figures ; 

 but as I omitted to draw up a description at the time, I have 

 borrowed the specific character from Meneghini." Ralfs. 



4. SCENEDESMUS OBTUSUS Menegh. 

 Plate XCII. Fig. 15. 



Char. Cells three to eight, ovate or oblong, with rounded ends, 

 and arranged alternately in two rows. 



Menegh. 1. c. p. 208. Scenedesmus quadraltcrnus Kiitz., 

 L c. p. 608. fig. 94. Scenedesmus octalternus Kiitz., 

 L c. p. 609. fig. 95. Arthrodesmus acutus Bailey, 

 Amer. Bacil. fig. 18?; Ralfs, in Annals, vol. xv. p. 404. 

 fig. 8. 



Hob. In boggy pools, Dolgelly : Ralfs. 



" The specimens I have examined did not agree in every 

 respect with the description and figures of this species, but 

 they probably belonged to it. The cells were ovate, the 

 broad ends of the rows placed alternately, the smaller ends 

 being in different directions ; sometimes the cells seemed only 

 held together by the hyaline matrix, in which state they 

 appear to connect the Desmidece, through Gonidium Ehr. 

 and Trochiscia Kiitz., with the Ulvacece. The cells of one 

 row are separated by the interposition of the broader ends of 

 the other." Ralfs. 



Note. Several of the figures of this family, especially certain of those 

 of the genera Euastrum and Cosmarium, are taken from those of Jenner 

 and Ralfs, illustrating the series of papers on the Desmidea inserted in 

 the " Annals." 



