Mr. J. Ralfs on the British Desmidiese. 189 



The outline of one of the segments has some resemblance to that 

 of a decanter. 



In the third section the fronds arc extremely minute, the seg- 

 ments are generally still less lobed than in the last, and the form 

 of the front view is more irregular and differs from that of the 

 preceding sections, especially in having an acute angle or process 

 at either the corners or sides of the terminal portion. 



* Segments of the frond deeply lobed; the terminal lobe cuneate, and 

 partly included in a notch formed by the -projection of the ends of the 

 lateral lobes. 



1 . E. verrucosum, Ehr. Frond rough with conic granules ; the seg- 

 ments three-lobed ; lobes broad, subcuneate, with a broad shallow 

 notch. Ehr. Infus. p. 162. tab. 12. fig. 5 j Pritch. Infus. p. 196. 

 fig. 125. Cosmarium verrucosum, Menegh. Synop. Desmid. in 

 Linnsea 1840, p. 222. 



Amongst aquatic plants in pools : rare. Cheshunt, Mr. Hassall ; 

 Weston Bog near Southampton, Rusthall Common, Kent, near Tun- 

 bridge Wells, and Ashdown Forest, Sussex, Mr. Jenner ; Penzance. 



Fronds compressed ; the segments which slightly diverge from 

 each other are broader than long, deeply three-lobed ; the lobes, 

 particularly the terminal one, broad and cuneate, and each has a 

 broad, shallow, terminal notch. Surface of the frond furnished 

 with numerous conic granules which give the margins a dentated 

 appearance : each segment has two prominences near the base ; 

 on these the granules form two or three concentric circles with a 

 granule in the centre; the terminal lobe has two similar but 

 smaller prominences. 



The side view, which is not so broad as the front one, is in- 

 flated at the base and attenuated upwards into a short neck, and 

 emarginate and slightly dilated at the end. The terminal lobe, 

 as seen by an end view, is four-lobed. 



This is a very beautiful species, and once seen, is not liable to 

 be confounded with any other British species, but may be easily 

 known by the conic granules covering the frond and giving a 

 dentate appearance to the outline. 



Plate VI. fig. 3. Euastrum verrucosum: a, front view; b, side view; 

 c, end view of terminal lobe. 



2. E. oblongum. Frond smooth, oblong ; segments five-lobed ; lobes 

 . broad, subcuneate, emarginate, the terminal one partly included 



in a notch. Euastrum Pecten, Ehr. Infus. p. 162. tab. 12. fig. 4 ; 



Pritch. Infus. p. 196. Echinella oblonga, Grev. in Hook. Br. Fl. 



vol. ii. p. 398 (1830). Cosmarium oblongum, Menegh. /. c. p. 221. 



Eutomia oblonga, Harv. Br. Alg. p. 188. 



In boggy pools. Warble ton, Sussex, and near Tunbridge Wells, 

 Weston Bog near Southampton, Mr. Jenner ; Penzance, Dolgelley 

 and Carnarvon. 



