)} 



422 SIR NICHOLAS YERMOLOFF OX SOME INTERMEDIATE FORMS 



metrical. Not subrostrate. Fusiform. Terminal fis- 

 sures comma-like turned in same direction. Area 

 linear-lanceolate. 

 Fig. 4. Navicula Monmouthiana-Stodderi (intermediate between 

 N. Monmouthiana and Cymbella Stodderi). Herkimer. 

 L. 0-07, B. O'Ol. Striae 20 in O'Ol mm., radiate, punc- 

 tate. Fusiform, nearly symmetrical. Ends slightly 

 subrostrate. Terminal fissures comma-like. Central 

 nodule slightly eccentric. 

 -,, 5. Cymhella Stodderi Cleve. Herkimer. L. 0*06. Striae 18 

 in O'Ol mm., punctate and radiate. Ends subrostrate. 

 Terminal fissures turned in same direction, comma-like. 

 Area lanceolate, not abruptly dilated towards centre. 

 Slightly asymmetrical. 



6. Cymhella Stodderi Cleve. Herkimer. L. 0-072, B. 0*01. 

 Striae 15 in 0*01 mm., radiate, punctate. Fusiform, 

 slightly asymmetrical. Ends subrostrate. Axial area 

 rather broad, lanceolate, not abruptly dilated toward 

 centre. Very near to N. Monmouthiana. 



7. Cymhella aequalis W. Sm. {suhaequalis Grun.). St. Fiore. 

 L. 0*04. Striae 10 in middle, 14 at ends, radiate, 

 decipient, puncta indistinct. Lanceolate, subrostrate. 

 Area just distinct. 



^, 8. Cymbella suhaequalis Grun. {aequalis W. Sm.). Premnay 

 Peat. L. 0'04. Striae 12-14 in O'Ol mm., radiate, 

 obscurely punctate, decipient. Ends obtuse or trun- 

 cate, subrostrate. Raphe almost straight surrounded by 

 hyaline zone rather broad, dilated round central nodule. 

 ,, 9. Cymhella angustata W. Sm. Herkimer. L. 0'04. Striae 

 16 in 0*01 mm., radiate, very faint. Ends rostrate- 

 capitate. Margins triundulate. Axial area narrow but 

 distinct. 

 ^, 10. Cymhella {Encyonema) gracilis Rabh. Monmouth, 

 Cherryfield. L. 0*06, B. 0*01. Striae 13 in 0*01 mm., 

 radiate, moniliform. Margins slightly triundulate. 

 Axial area linear, central area absent. Raphe slightly 

 nearer to ventral margin. Central nodule on dorsal 

 side. Ends subrostrate. Terminal nodules slightly 

 distant from acute ends. Striae on fossil forms robust ; 

 median stria on ventral side with indistinct stigma. 



>5 



