420 DIATOMACE^. 



Section ii. 

 Frond stipitate. 



A. Frustules loedge-shaped, 



75. GOMPHONEMA ^^. 



Char. Frustules cuneate, solitary or geminate^ supported on 

 a simple or branched and attached filiform stipes. 



Derivation. From 'yofi^os, a wedge, and viiixa, a thread. 



The extremities of the frustules in the front view are 

 punctated and truncated, but in the lateral aspect rounded 

 or pointed ; the frustules are for the most part striated late- 

 rally, the strife being interrupted by a longitudinal pellucid 

 line, in the centre of which is a depression often assuming 

 the appearance of a foramen. The genus bears a close re- 

 lation to the genera Stgllaria and Lichmophora, the former 

 genus differing only from Gomphonema in the frustules being 

 invariably sessile, and the latter in having several frustules 

 associated together at the end of each branch of the stij^es, 

 and forming a fan- like expansion. 



The species of the genus Gomphonema are usually found 

 in freshwater. 



a. Frustules in lateral view constricted heloio the apex, so as 



to appear urn-shaped. 



1. Gomphonema geminatum Ag. 



Plate XCVIII. Fig. 1. 



Cha?\ Stipes much branched, tufted. Frustules large, cu- 

 neate, often geminate, puncta at the end obsolete. Lateral 

 surfaces urn-shaped, str^iated. Stria) radiating. 



Ag. Syst. p. 12.; Conspect. Diatom, p. 35.; Grev. Crypt. 

 Fl. t. 244. f. 2.; Kiitz. Synop. Diatom, in Llnna3a, 1833, 

 p. 569. ; Harv. British Algie, p. 207. Gomph. ampul- 

 laceum Grev., in Hook. Br. Fl. p. 410. G. geminatum 

 Ralfs, in Annals, vol. xii. p. 460. pi. xvili. fig. 3. 



