8 Transactions of the Society. 



to the laws of priority in nomenclature in use among phanero- 

 gamic botanists, his name excludes Dixon's Tefrachastrum. The 

 complete absence of radiating lobes and of marginal incisions, as 

 noted by Hassall, separates it well from Micrasterias. The general 

 form and the thickness of the frond seems to me indeed to bring 

 it nearer to Euastrum, which genus it approaches through 

 E. pecti7iatum. The most perfectly developed form is that repre- 

 sented in fig. 7, which is not, however, drawn by either Hassall, 

 Ealfs, or "WoUe. The apical segment is bidentate ; the basal 

 segment bidentate at the base, and with an additional tooth on the 

 shoulder ; but any or all of the teeth may be wanting ; and that 

 this does not constitute specific difierence is seen by the frequent 

 occurrence of specimens, as shown in fig. 8, in which the two 

 halves exhibit this character in very different degrees. Fig. 9 

 represents an individual dividing. The cell-wall is finely punctate, 

 as shown in fig. 10. The size is as variable as the form. In the 

 specimen figured, the length of the frond is 175 /x ; breadth of 

 basal segment, 140 ^ ; of apical segment, 115 fi; breadth of isthmus, 

 35 yu, ; width of neck, 55 /j,. Both Ealfs's and Wolle's measurements 

 are smaller ; but I have seen specimens considerably larger. 



"Very common in bog pools. In the genus Eolocystis I should 

 include Micrasterias pinnatijida Ealfs, M. laticejos Nords., M. 

 Eitchelii Wolle, and M. disputata Wood (probably none of these 

 are specifically distinct) ; also Euastrum intermedium Cleve, 

 and var. cuspidatum WoUe, and E. urnseforme Wolle. 



Euastrum verrucosum Ehrb. Yewdale Fells, Lancashire, 

 and Ambleside. 

 „ oblongum Grrev. 



„ multilohatum Wood (' Fresh- water Algse of 



North America,' p. 135, t. xii. f. 10). Fig. 11. 



Length of frond, 90 /a; breadth, 65 /a; breadth of isthmus, 

 25 /i. Differs from E. oUongum in its smaller size and in the 

 more horizontal direction of the lobes, but agrees in general out- 

 hne. The terminal lobe is also quite undivided by any vertical 

 incision. The specimens observed by me correspond very closely 

 to Wood's description and figure ; the species has apparently not 

 been observed before in Europe. Bog pool, Loughrigg. 



Euastrum crassum Breb. 

 „ pinnatum Ealfs. 

 „ affine Ealfs. 

 „ ampuUaceum Ealfs. 

 „ insigne Hass. 

 „ cuneatum Jen. 



This seems to me a very well-marked species. 



