- 34 - 



32. Pinnularia sp. tab. nostr., fig. 8. 



L. 0,049 mm., B. 0,oi mm. Striæ 10 in 0,01 mm. 



Valve rectilinear with rounded apices. Terminal fissures comma- 

 shaped. Apical area narrow. Striæ parallel, at right angles to the 

 apical axis, absent in the middle, so that a transapical area arises. 



As I have seen but one specimen of this small form, I dare not 

 regard it as a distinct species. It seems to be nearest to Pinn, macilenta 

 (Ehr.) Gl. 



Amphora Ehr. (1840). Cl. Syn. II, p. 99. 



33. A. acutiuscula Ktz. V. H. Syn. tab. I, fig. 18. 

 Solitary in a sample from Lem Dan. 



Area: Greenland, Spitzbergen, Europe,. Madeira, New Zealand, Samoa. 



Aclmanthes GI. Syn. H, p. 163. 



Actinoneis Gl. 1. c. p. 185. 



34. A. oblongella Öst. nov. sp. tab. nostr., fig. 9. 

 L. 0,057 mm., B. 0,006 mm. 



Epitheca: apical area narrow, 10 striæ in 0,01 mm., finely 

 transversely lineated. Hypotheca: striæ very fine, slightly curved. 

 Central area narrow. 



Hypotheca of this small species highly reminds of Navicula 

 Bokeana Grun. var. oblongella Grün. (V. H., Syn. tab. XIV, fig. 21). 

 But as I have seen both valves in situ, I am quite sure it is an 

 Achnanthes. 



Klong Majum. 



In the same sample where Ach. oblongella occurs I found a small 

 form, which I have figured in tab. nostr., fig. 10. 



Valve oblong elliptical, L. 0,018 mm., B. 0,007 mm., striæ 10 in 

 0,01 mm., somewhat shortened so that an apical area arises. In 

 specimens mounted in styrax it was impossible to see any raphe, 

 but in a dry specimen I could catch a glimpse of a such one with 

 distant central pores. As to the structure of the valve all the spe- 

 cimens examined were identical. Thus I dare not decide if the 

 present form is an Achnanthes or a Navicula. 



Microneis Gl. 1. c. II, p. 187. 



35. A. minutissima Ktz. V. H. Syn. tab. XXVII, figs. 37-38. 

 Klong Majum, Klong Munsé, Lem Dan. (4 samples). 



var. cryptocephala Grun. V. H. 1. c. figs. 41 — 44. 

 Klong Prao, Klong Munsé, Lem Dan. 



Area: the main species: Greenland, Europa, Mongolia, var. cryptocephala 

 according to Cleve (I. c. p. 188) Finland. I have found it in the Færo Islands 

 and in Denmark. 



