GOMI'HONEMA. 423 



b. Lateral surfaces not constricted below the apex. 



4. GOMPHONEMA CRISTATUM Ralfs. 



Plate C. Fig. 1. 



Char. Frustules crested^ not constricted below the apex, striated 

 laterally. 



Gomphoncma cristatum Ralfs, iu Annals, vol. xii. p. 463. 



pi. xviii. fig. 6. ; Jenner, in loc. cit. p. 206. 

 Hah. On Conferva glomerata in a stream near Shorcham, 



Kent, Dec. 1842. Farnham, Surrey : Mr. Jenner. 



The only species with which this beautiful Gomphonema 

 could be confounded is G. acuminatum, from which it differs 

 in being altogether a smaller plant, and in the absence of the 

 constriction below the apex. 



For its discovery naturalists are indebted to JNIr. Jenner. 



5. GOMPnONElMA DICUOTOMUJM Kiltz. 



Plate XCIX. Fig. 2. 



Char. Frustules linear, cuneoie in front view, xoith very minute 

 terminal imncta. Lateral surfaces lanceolate, faintly 

 striated. 



Kiitz. Synops. Diatom, p. 569. fig. 48. ; Ralfs, in Annals, 

 vol. xii. p. 463. pi. xviii. fig. 7. Gomph. gracile Ehr., 

 Die Infus. p. 217. t. 18. fig. 3. ; Pritch. Lifus. p. 227. 

 G. angustum? Ag., 1831. 



Hab. Trengwainton ponds, near Penzance : Mr. Ralfs. 



The frustules of this species somewhat resemble those of 

 Gomphonema Berkeleyi, but they are more elongated, nar- 

 rower, often nearly linear, and their lateral surface lanceolate, 

 and not clavate. 



6. Gomphonema Berkeleyi Grev. 



Plate C. Fig. 2. 



Char. Frond forming large mucous masses. Stipes branched, 



E E 4 



