426 DIATOMACE^. 



Derivation. From kokkos, a grain, and vrjixa, a thread. 



The frustules in this genus may be compared to a grain of 

 wheat in form. 



1. COCCONEMA LANCEOLATUM Ehr. 



Plate CI. Fig. 1. 

 Char. Frustules large, semi-lanceolate, straight, obtuse, 



Gomjjhonema lanceolatum Agardh, Conspect. Crit. Diatom. 

 1831, p. 34. Gomphonema (Paltonophora) lanceolatum 

 Klitz., in Linnaea, 1833, p. 38. ; Jenner, in Flora of 

 Tunbrido'e Wells. Cocconema lanceolatum Ehr., Die 

 Infus. p. 224. pi. xix. fig. 6. 



Hah. Waterfall at Hill Park, Westerham, and at Shore- 

 ham, Kent ; Parham, near Pulborough, &c. : Mr. Jenner. 

 Cheshunt : A. H. H. 



This is a very fine and distinct species. 



2. Cocconema cymbifokme Ehr. 

 Plate CI. Fig. 2. 



Char. Frustules slightly curved, narroic, attenuated, sub- 

 acute. 



F?'ustuliacgmbiformislLiitz.,iiiluirmiXia, 1833, p. 540. t. 15. 

 fig. 9. Cocconema cymbifoi^me Ehr., Die Infus. p. 225. 

 pi. xix. f. 8. ; Jenner, in Fl. of Tunbridge WeUs. 



Hab. New River reservoir, Cheshunt : A. H. H. 



This species might readily be confounded with the previous 

 one, from which it is to be distinguished by its smaller, nar- 

 rower, more attenuated and somewhat curved frustules. 



3. Cocconema cistula Ehr. 



Plate CI. Fig. 3. 



Char. Frustules crescentic, ventricose, obtuse, often in pairs. 



