Mr. J. Ralfs on the British Desmidiese. 193 



Salwey ; 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. 6. Euastrum spinosum: 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. 

 a. 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, Sussex, 

 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, slightly contracted upwards and rather dilated at the end ; 

 the terminal notch forms a concavity between the two acute 

 angles. 



The variety /?, 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 binale ; b, var. /3. 

 Analysis. 



{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- 



2,< tated appearance to the outline verrucosum. 



[ Frond minutely punctate 3 



„ J* Segments distinctly 5-lobed, all the lobes emarginate ... oblong am. 

 *\ Segments 3-lobed Pelta. 



