EUASTRUM. 381 



compressed, dotted. Segments m front view three-lohed; 

 lateral lobes each twice slightly emarginate : in lateral view 

 much compi^essed. 

 Cosmarium Pelta Corda, Almanac de Carlsbad, p. 121. C. 

 Pelta INIenegh., Synops. Dcsmid. p. 222. Eiiastrum 

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

 loc. cit. p. 198. 

 Hab. 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. EUASTEUM DiDELTA Ralfs. 



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



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

 Segments in front view pyramidal, and laterally 7i$ually 

 twice emarginate ; in ixa.x\s\erse. somewhat four-lobed, and 

 in end view oval. 



Heterocarpella Didelta Turp.,Mem. p. 295. (1828). Hetero^ 

 carpclla polymorpha Kiitz., Synops. Diatom, in Linnosa, 

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

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

 Infus. 13. 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. 219. Euastrum Didelta 

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

 of Tunbridge Wells, p. 198, 



Hab. Frequent in Sussex : Mr. Jenner. Hcnfield : Mr. 

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

 T. Sahcey. Caernarvon ; Dolgelly, near Carmarthen ; 

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



A very distinct species. 



