BIHANQ TILL K. SV. VET.-AKAD. HANDL. BAND. 21. AFD. III. N:0 2. 33 



United them. On tlie other hand this species frequently 

 approaches E. praerupta Ehb., from wliich it is distinguished 

 chiefly by its mucli closer striae. 



E. tenella Grun. — V. H. XXXIV, 5, 6, 9. 



Valve more or less arcuate, 0,012 to 0,02.5 mm. in length, 

 0,003 to 0,00 8 mm. in breadth, witli truncate ends. Striae 

 18 in 0,01 mm. 



Nu. 3, 18, 19, 37, 39, V. 12, Na. 35, Gl. 43, Gl. D. 45.— 

 Somewhat frequent. 



This small species is very like E. exigua Bréb. in V. H. 

 XXXIV, 11, but the latter has much closer striae: 27 in 0,oi 

 mm. according to the figure. It is nearly akin to E. arcus 

 Ehb. but is much smaller and has closer striae, for which 

 reason it has been made a difPerent species. 



E. Nymaniiiana Grun. — V. H. XXXIV, 8. — Pl. I, 36. 



Valve arcuate to almost straight, linear, 0,02.5 to 0,0.35 

 mm. in length. O, o 0.3 mm. in breadth. Ends of the valve 

 characteristic, acutely protracted towards the dorsal side. 

 Striae 21 in 0,oi mm. 



Nu. 2, 3, 5, 11, 18, 19, 39. Kv. 28, S.-K. 22, 33, Jm. 31, 

 Na. 35, Gl. 43, 47. — Frequent. 



E. fallax A. Cl. n. sp. — Pl. I, 35. 



The valve has the same outline and size (O, o 2 mm. in 

 length) as E. Nymanniana Grun., but the striae are only 14 

 to 15 in 0,01 mm. 



Nu. 5, 35, 37. — Rather rare. 



E. praerupta Ehb. 



Ends of the valve abruptly truncate. Striae coarse, at 

 unequal distances, 7 to 12 in 0, 01 mm. 



The typical form has 7 to 8 striae in 0,oi mm. The 

 valve is O, o 4 to 0,0 7 mm. in length, 0,012 to 0,oi5 mm. in 

 breadth. — V. H. XXXIV, 18, 19. 



Kv. 1, 26, 28, 32, Nu. 2, 5, 11, 14, 18, 19, 25, 37, 39, 41, 

 S.-K. 7, 22, 33, Jm. 6, 31, Km. 10, Na. 35, Gl. 43, Gl. D. 

 44, 45, Ke. 49. — Frequent. 



f. curta Grun. - V. H. XXXIV, 23, 24. 



Length of the valve O,.' 3 mm. 



Kv. 26, Nu. 18, 37. — Rather rare. 



3 



