STAURASTRUM . 125 



ENGLAND. Scawfell, Cumberland ! Easclale and 

 Stickle Tarns, Westmoreland ! Old Cote Moor and 

 Cam Fell, W. Yorks ! Bog near Widdale Beck, N. 

 Yorks ! Dartmoor, Devonshire (Joshua). 



WALES. Moel Siabod and Llyn Bochlwyd, Carnar- 

 vonsliire ! Dolgelly, Merioneth ! 



IEKLAND. Kylemore, Galway ! Carrantuohill and 

 Lower Lake of Killarney, Kerry ! 



Geot/r. Distribution- -France. Germany. Austria 

 and Galicia. Servia. Italy. Norway. Poland. 

 Greenland. Azores. 



With regard to the Desmids described under the names of 

 St. Capitulum, St. amoenum, and St. pileolatum, a few plain 

 statements are necessary. The original descriptions of St. 

 Capitulum and St. pileolatum are very brief and imperfect, but 

 the outlines of the figures are moderately good. St. amoenum 

 appears to have been founded upon a misconception of the 

 true nature of St. Capitulum a misconception which we 

 venture to think was due entirely to the failure of the 

 author to realise that the figure given by Ralfs was inaccurate 

 in its detail. This figure was only a copy of one of 

 Brebisson's drawings, and nearly all that author's figures 

 are very inaccurate, the detail being invariably wrong. 



We have a wide acquaintance with these forms of 

 Staurastrum in the British Islands and in western Europe 

 generally, and have come to the conclusion that it is only 

 possible to recognize two species. These must of necessity be 

 referred to St. Capitulum and St. pileolatum, the two 

 originally described and so poorly figured by Brebisson in 

 the Appendix to RalfV i British Desmids/ A comparison of 

 a large series of specimens with all the published information 

 on these Desmids convinces us that no other interpretation 

 would be consistent with the known facts. 



These two species are distinct only by reason of the 

 direction of the apical angles of the semicell, w T hich in St. 

 Capitulum are horizontally spreading whereas in St. pileolatum 

 they are upwardly directed. 



In addition to what we regard as the type form the 

 following varieties of this species can be distinguished, of 

 which only the first is at present known to occur in the 

 British Islands : 



Var. SPETSBKRGENSE (Nordst.) Cooke, Brit. Desin. 1887, 

 p. 161, t. 55, f. 3. For description see below. 



