Mr. J. Ralfs on the British Desmidiese. 193 



Salioey ; Mayfield and elsewhere in Sussex, near Southampton ; Mr. 

 Jenner ; Dolgelley, Penzance. 



Fronds very minute, about twice as long as broad ; segments 

 scarcely lobed, the base slightly emarginate at each side, not con- 

 tracted into a neck, but with an acute, short, spine-like process on 

 each side near the end ; the end itself is produced beyond these 

 spines and rounded ; the notch is rather deep and slightly gaping. 

 Sometimes the base has one or two spine-like projections on each 

 side. 



This species differs from Euastrum rostratum in not being con- 

 tracted into a neck, and in its prominent pouting extremity, which 

 is not at all angular beyond the lateral spines. 



Plate VII. fig. G. Euastrum sp'mosnm: a, front view; b, end view; 

 c, fronds dividing. 



9. E. binale. Segments concave or truncate at the end, not pro- 

 jecting beyond the acute angles. Heterocarpella binalis, Turp. ; 

 Kutz. /. c. p. 70. Cosmarium binale, Menegh. /. c. p. 221. 

 o. Segments inflated at the base; the notch broad, forming a con- 

 cavity between the angles. 

 /S. truncatum. Fronds quadrilateral ; the end truncate, acute at the 

 angles, with a small triangular notch in the middle. 

 In fresh- water pools. Mayfield and Piltdown Common, Sus^sex, 

 Mr. Jenner ; Dolgelley, Penzance. 



Fronds very minute, about twice as long as broad ; segments 

 inflated at the base, either entire or somewhat bicrenate at the 

 sides, shghtly contracted upwards and rather dilated at the end ; 

 the terminal notch forms a concavity between the two acute 

 angles. 



The variety /3, which may prove distinct, differs in being qua- 

 drilateral, and still more in having truncate ends with a small 

 but distinct notch in the centre ; the angles are acute, and slightly 

 project laterally ; the sides of the segments are generally a little 

 crenate. 



This species is easily distinguished from the two preceding- 

 ones by its concave or truncate ends and its notch, the sides of 

 which do not project beyond the lateral spines or angles. 

 Plate VII. fig. 7. a, Euastrum linale ; h, var. /3. 

 A7ialijsis, 



{Terminal lobes distinct, cuneate, partly included in a notch 

 formed by the lateral lobes 2 

 Terminal lobe not included in a notch 4 



{Frond rough with large conic granules, which give a den- 

 tated appearance to the outline verrucosum. 

 Frond minutely punctate 3 



o f Segments distinctly 5-lobed, all the lobes emarginate ... obloiujum. 

 '\ Segments 3-lobcd Pdta. 



