P. T. Cleve: The Diatoms of Finland. 35 



Sectio: Lyrce. 



N. hyalina Donk. 

 Sinf. Nyl. (Dannf.). 



Sectio: Formosce. 



N. formosa Greg. — T. M. S. IV, V, 5. 



Mb. Ab. 100. 



Var. holmiensis CI. — N. R. D. II, 18. 



This form has coarser striae (on finnish specimens 10 in 

 0,oi m. m.) than N. formosa (14 striae in 0,01 m. m.), a larger 

 area and a very indistinct line crossing the striae. 



Mb. Ab. 100. 



N. hebes Ralfs. — Donk. B. D. Ill, 12. 



Lim. 21, 23, 26, Lt. 32, 33. 



This species is a northern or alpine form. 



N. perpusilla Grun. — V. H. XIV, 22, 23. 



Ab. 52, 53, Lim. 22. 



N. trinodis W. Sm. — V. H. XIV, 31. 



Ab. 54. 



N. ladogensis CI. n. sp. — Valve broadly lanceolate, with 

 subrostrate ends, 0,0 2 5 in. m. in length and 0,oi4 m. m. in breadth. 

 Striae slightly radiant, 17 in O,oi m. m., finely punctate, shortened 

 around the central nodule, where is a broad, transverse area. 



PL II, fig. 3. 



Lad. 62 (rare). 



N. amphisbaena Bory. — V. H. XI, 7. 



Mb. Ab. 100. 



Var. subsalina Sinf. Nyl. (Dannf.). 



Var. Fenzlii Sinf. Nyl. (Dannf.). 



N. depressa CI. n. sp. — Valve elliptic, with rostrate ends, 

 0,0 2 2 m. m. in length and 0,009 m. m. in breadth. The surface 

 of the valve has four depressed areas, so that the margins and 

 the parts around the median line and the central nodule are 

 higher. The valve is covered with line striae, 27 in O,oi m. in., 

 more distant (about 24 in 0,oi m. m.) on the middle of the valve, 

 slightly radiant, especially near the ends. The stria' reach the 



