26 Acta Societatis pro Fauna et Flora fennica. VIII, n. 2. 



in north Iceland and at Cape Deschneff (north-eastern corner of 

 Asia). It appears consequently to be a northern form. 



Sb. 2, 8, 16, Lad. 85, Lim. 20, 21, 23, Lt 29, 30, 32, 34. 



Var. interrupta CI. — Smaller than the typical form (0,0 6 

 m. m. in length and 0,oi m. m. in breadth). Striae interrupted 

 on the middle of the valve, about 12 in 0,oi m. m., strongly di- 

 vergent. 



PL 1, fig. 10. 



Sb. 8. 



P. brevistriata Grun. — V. H. VI, 5. — Pin. biglobosa Schum. 

 II, II, 48. 



Ab. 49, Sb. 2, 7, 17. 



Foss. Tb. 90, Ob. 92. 



P. stauroptera Grun. — V. H. VI, 7. — Nav. parva V. H. 

 VI, 6. — Nav. tabellaria var. stauroneiformis V. H. VI, 8. — 

 Nav. gibba Donk. B. D. XII, 3. - Nav. gibba A. S. XLV, 48, 49, 

 50, 51. 



A great confusion exists about Navicula gibba and N. stau- 

 roptera. Pinn. gibba in W. Sm. B. D. XIX, 180, has 11 striae in 

 0,oi m. m. and a narrow area. I think this form may be taken as 

 the type and if so the true P. gibba has not been found in Fin- 

 land. This form, determined by Grunow in CI. & M. D. n:o 291 

 as N. gibba var. acrosphseria, is comparatively rare. There can 

 be no doubt that Nav. gibba, N. parva, N. stauroptera and. N. ta- 

 bellaria in Van Heurcks Synopsis are only forms of one and the 

 same species, for which I propose the name of P. stauroptera. P. 

 stauroptera is larger than P. gibba and measures 0,0 9 5 to 0,15 

 m. m. in length and 0,oi to 0,oi5 m. m. in breadth. The striae 

 are short and divergent, 9,5 to 10 in 0,oi m. m., continuous or 

 interrupted on one or both sides of the central nodule. The area 

 is broad. The end-fissures are semicircular. 



Ab. 36, Sb. 2, 5, 6, 8, 10, 16, Lim. 25. 



Foss. Nyl. 87, Sa. 88, 89, Ta. 94, 96, 97, Tb. 90, Ob. 92, 

 Lk. 104. 



P. Brandelii CI. n. sp. — Valve linear, with subundulate 

 margins and broadly rounded, sometimes subclavate ends, 0,0 7 to 

 0,0 8 m. m. in length and 0,o 7 to 0,oo9 m. m. in breadth. The 

 striae are divergent, interrupted in the middle of the valve, 14 in 



