432 DIATOMACE^. 



Hah. Gardener Street : Mr. Jenner. 



Through this and the following species the genus Navicula 

 seems to pass into that of Cymhella, in wliicli genus indeed 

 the striated Navicula would not be very improperly placed. 



7. Navicula gibba Ehr. 

 Plate CII. Fig. 4. 



Char. Frustules in lateral view straight, narroiv, injlated; near 



the centre gibbous. 

 Navicula gibba, N. unciata, Abhandl. der Akademie d. 



Wissensch, zu Berlin, 1830, p. 64, 65. 68. 1831, p. 80. 



Frustulia incrassata Kiitzing, Linna^a, 1833, p. 545. 



t. xiii. fig. 17. Navicula gibba, Die Infus. p. 184. t. xiii. 



f. 19. ; Jenner, in Fl. of Tunbridge Wells, p. 204. 

 Hab. Cheshunt : A. H. H. Ashdown Forest : Jack's 



Wood Spring ; Chiltington Common, near Pulborongh, 



&c. : Mr. Jenner. 



8. Navicula lanceolata Ehr. 

 Plate CII. Fig. 14. 

 Char. Frustules lanceolate, extremities subacute. 



Frustulia lanceolata Klltz., in Linncea, 1833, p. 14. t. xiii. 

 f. 13. Navicula lanceolata Ehr., Die Infus. p. 185. 

 t.xiii. fig. 21. 

 Hab. Sussex : ilfr. Jenner. 

 A well-marked little species. 



80. EXILAKIA Grev. 



Char. Frustules elongated, at first attached by a sessile and 

 undivided stipes, subsequently free, radiated, single, or bi- 

 nate. Junction surfaces frequejitly striated. 

 Derivation. From exilio, to issue forth ; in allusion to the 

 radiate disposition of the frustules. 



