28 ASTRID CLEVE, ON RECENT FRESHWATER DIATOMS. 



E. mouodon Ehb. — V. H. XXXIII, 8. 



Valve tapering from the middle to tlie slightly protracted, 

 rounded ends, 0,08 to 0, 09 mm. in length, 0,oi6 mm. in breadth. 

 Striae eqnidistant, 12 in 0,oi mm. 



Kv. 1, 32, Nn. 17, 18, Jm. 6, Gl. 17. — Somewhat rare. 



This species is sometimes difficult to distingnish from 

 E. major Rabh. 



E. diodon Ehb. var. minor Grun. — V. H. XXXIII, 5. 



Length of the valve (),05 to 0,o6 mm. Striae 12 to 14 in 

 0,01 mm., eqnidistant. 



Nu. ö, 19, 25, Jm. (>, 31, Ks. 15, 20, Tj. 42, Gl. 43. — 

 Rather freqnent. 



Var. diminuta Grun. — V. H. XXXIII, 7. 



Length of the valve 0,o2 to O, o 3.") mm. Striae 14 in 

 0,01 mm. 



Kv. 2S, 34, Nn. 14, 18, 37, Ks. 20, S.-K. 33. — Somewhat 

 freqnent. 



I think this species may inclnde E. bidentnla W. Sm. as 

 a variety. The latter gradnates to E. diodon var. minor 

 Grun., from which it is distingnished only by the narrower 

 shape and somewhat closer striae, 17 to 18 in 0,oi mm. 



E. robusta Ehb. 



Valve arcnate, with rostrate ends. Striae partly not 

 reaching the ventral margin, 10 to 11 in 0,oi mm. 



Var. tctraodon Ralfs. — V. H. XXXIII, 11. 



Ks. 15, 20, Kv. 32, Jm. (1. — Somewhat rare. 



Var. diadeuia Ralfs. — V. H. XXXIII, 12. 



Kv. 1, Jm. 6, Ks. 15, 20, S.-K. 22, Tr. 38, Ll. 21, Nu. 41, 

 Ke. 49. — Somewhat freqnent. 



Var. hendecaodon Ralfs. — V. H. XXXIII, 13. 



Jm. 6, Ks. 15. — Rare. 



E. tridentula Ehb. var. permlnuta Grun. — V. H. XXXIV, 30. 

 f. 3- to 4-dentat8e. Striae 17 in 0, 01 mm. 



Nu. 2, 18, Na. 35, Gl. D. 44. — Rare. 



E. parallela Ehb. — V. H. XXXIV. K). 



Valve arcnate, linear, with non-protracted, rounded obtuse 

 ends. Striae 11 to 12 in 0, 01 mm. End-nodules at the ends 

 of the valve. 



