GOMPHONEMA. 423 



b. Lateral surfaces not constricted below the apex. 



4. GOMPHONEMA CRISTATUM Rolfs. 



Plate C. Fig. 1. 



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



laterally. 



Gomphonema cristatum Ralfs, in Annals, vol. xii. p. 463. 

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



Hob. On Conferva glomerata in a stream near Shoreham, 

 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 Mr. Jenner. 



5. GOMPHONEMA DICHOTOMUM Kutz. 



Plate XCIX. Fig. 2. 



Char. Frustules linear, cuneate in front view, with very minute . 

 terminal puncta. 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. Infus. 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 



