J) 



5> 

 >J 



55 

 J5 



OF THE GENERA NAVICULA AND CYMBELLA. 421 



to some : on the contrary, they are necessary, and fruitful of 

 larger results, and every Systematist, with his minute and 

 laborious examinations, brings his contribution towards the; 

 construction of the great building of scientific knowledge. 



Description of Plates 26-28. 



Plate 26. 



Fig. 1. Navicula Momnouthiana Grun. 



2. Navicula Monmouthiana Grun. 



3. Navicula Monmouthiana- Stodderi. 



4. Cymhella Stodderi Cleve. 



5. Cymhella Stodderi Cleve. 



6. Cymhella aequalis W. Sm. 



7. Cymhella aequalis W. Sm. 



8. Cymhella angustata W. Sm. 



9. Cymhella {Encyonema) gracilis Rabh. 



10. Cymhella [Encyonema) Scotica W. Sm. 



11. Cymhella delicatula Kiitz. 



12. Cymhella {Encyonema) graciUs-Cesatii. 



13. Cymhella Cesatii Rabh. 



,, 14. Cymhella microcephala Grun. 



Plate 27. 



(Magnification : Figs. 1-9, x 1200 ; Fig. 10, x 700.) 



Fig. 1. Navicula Monmouthiana Giun. Type form (Cleve). Mon- 

 mouth. L. 0-07, B. 0-01. Fusiform. Striae 16 (middle) 

 to 20 (ends) in O'Ol mm., nearly parallel in middle, 

 radiate at ends. Central pores distant. Area regu- 

 larly linear or rather parallel to margins. Ends show 

 no tendency to subrostration. 

 ,, 2. Navicula Monmouthiana Grun. Monmouth, Cherryfield. 

 . L. 0-07, B. 0-01. Striae 16-20 to O'Ol mm., parallel in 

 middle, radiate towards ends ; ends not subrostrate, 

 though showing sometimes a tendency to subrostration. 

 Area linear-lanceolate. 

 3. Navicula Monmouthiana- Stodderi {Navicula Monmouthi- 

 ana nearly passing into Cymhella Stodderi) . Herkimer. 

 L. 0*05. Striae 18 to O'Ol mm., punctate and radiate. 

 Raphe nearly straight. Pores distant. Nearly sym- 



5 5 

 55 

 55 



)5 



