NAVICULA. 431 



Hob. Cheshunt : A. H. H. Aberdeen : Dr. Dickie. 

 A very well marked species. 



4. NAVICULA PLATYSTOMA Ehr. 

 Plate CII. Fig. 6. 



Char. Frustules elongated, quadrangular, with straight sides, 



rostrated at each end. 

 Hob. Cheshunt: A.H.H. 

 Die Infus. p. 178. t. xiii. fig. 8. 



A distinct and not uncommon species. 



b. Frustules striated. 



5. NAVICULA NODOSA Ehr. 



Plate CII. Fig. 7. 



Char. Frustules small, in side view thrice undulated, ros- 

 trated at each extremity. 



Die Infus. t. xiii. fig. 9. Frustulia nodosa ? Jenner, in 

 Fl. of Tunbridge Wells, p. 204. 



Hab. On Ashdown Forest, near Forest Row, between 

 Gardener Street and Hailsham, &c. : Mr. Jenner. 



Mr. Jenner remarks that his specimens agree with Ehren- 

 berg's description and figures in every respect save that the 

 frustules were striated. It is probable that Ehrenberg 

 overlooked the striae, and that these are always present. 



6. NAVICULA IK&QUALIS Ehr. 

 Plate CII. Fig. 13. 



Char. Frustules in front view attenuated, towards each end 

 truncate ; in side aspect unequal. 



Navicula incequalis, Bericht. der Akademie d. Wissensch. 

 zu Berlin, 1836, p. 53. ; Die Infus. p. 184. t. xiii. f. 18. 



