EUA8TRUM. 381 



compressed, dotted. Segments in front view three-lobed ; 

 lateral lobes each twice slightly emarginate : in lateral view 

 much compressed. 



Cosmarium Pelta Corda, Almanac de Carlsbad, p. 121. (7. 

 Pelta Menegh., Synops. Desmid. p. 222. Euastrum 

 Pelta Ralfs, in Annals, vol. xiv. pi. vii. f. 1. ; Jenner, 

 loc. cit. p. 198. 



Hob. Bogs at Fisher's Castle and on Ashdown Forest ; 

 Piltdown Common : Mr. Jenner. Dolgelly ; Penzance : 

 Mr. Ralfs. High Beech : A. H. H. 



There is no other species with which this need be con- 

 trasted. 



4. EUASTRUM DIDELTA Ralfs. 

 Plate XC. Fig. 8., and Plate XCI. Fig. 11. 



Char. Frond about three times as long as broad, dotted. 

 Segments in front view pyramidal, and laterally usually 

 twice emarginate; in transverse somewhat four-lobed, and 

 in end view oval. 



Heterocarpetta Didelta Turp.,Mem. p. 295. (1828). Hetero- 

 carpellapolymorpha}L\Mz., Synops. Diatom, in Linnaea, 

 1833, p. 70. fig. 82. Euastrum ansatum, Abhandl. d. 

 Akademie Wissensch. zu Berlin, 1831, p. 82. ; Ehr. 

 Infus. p. 162. t. 12. fig. 6. Cosmarium lagenarium, Al- 

 manac de Carlsbad, 1835, p. 206. pi. ii. fig. 26. Cos- 

 marium Didelta Menegh., 1. c. p. 2 1 9. Euastrum Didelta 

 Ralfs, in Annals, vol. xiv. pi. vii. fig. 2. ; Jenner, in Flora 

 of Tunbridge Wells, p. 198, 



Hob. Frequent in Sussex : Mr. Jenner. Henfield : Mr. 

 Borrer. Cheshunt : A. H. H. Barmouth Road : Rev. 

 T. Salwey. Caernarvon ; Dolgelly, near Carmarthen ; 

 and Penzance : Mr. Ralfs. Aberdeen : Dr. Dickie. 



A very distinct species. 



