426 DIATOMACE^. 



Derivation. From KOKKOS, a grain, and vrjfjua, a thread. 



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

 wheat in form. 



1. COCCONEMA LANCEOLATUM JEhr. 



Plate CI. Fig. 1. 

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



Gomphonema lanceolatum Agardh, Conspect. Crit. Diatom. 

 1831, p. 34. Gomphonema (Paltonophora) lanceolatum 

 Ktitz., in Linneea, 1833, p. 38. ; Jenner, in Flora of 

 Tunbridge Wells. Cocconema lanceolatum Ehr., Die 

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



Hob. 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, narrow, attenuated, sub- 

 acute. 



FrustuliacymbiformislLuiz., inLinnaea, 1833, p. 540. t. 15. 



fig. 9. Cocconema cymbiforme Ehr., Die Infus. p. 225. 



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

 Hob. New Kiver 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. 



