KONGL. SV. VET. AKADEMJENS HANDLINGAR. BAND 26. N:0 2. 145 



Forma arctica. Stauros narrow. Striae 19 to 21 in 0,oi mm. — S. pellucida Cl. Vega 

 p. 475 PL XXXV f. 10. 



Marine: Cape Wankarema (North Siberian Sea)! 



Forma mediterranea. Stauros broad, irregularly subquadrate. Striae 16 in 0,oi mm. 



Marine: Barcelona! Balearic Islands! 



This is a curious form, not closely connected with any other known species, so that its 

 position in a natural system is uncertain. I have placed it here only provisionally. It always 

 occurs very sparingly. 



2. S. (libellus) constricta (Ehb. 1843?), W. Sm. (1853). — V. membranaceous, linear, 

 convex, sometimes constricted in the middle, with subacute, rounded or subcuneate ends. L. 0,05 to 

 0.14; B. 0,00 7 5 mm. Stauros pervious, narrow linear. Axial area indistinct. Striae 25 to 27 in 

 0,01 mm. transverse. Frustnle with complex connecting zone. — • Stauron. constricta Ehb. Am. 

 PI. I: 2 f. 12 b.? Amphiprora constricta W. Sm. B. D. I PL XV f. 126. Stauron. amphoroides 

 Grun. in A. S. Atl. XXVI f. 35 to 39. JSav. simiilans Donk. B. D. p. 60 PL IX f. 3 (1873)? 



Marine or brackish: Davis Strait! North Sea (coasts of Sweden, England, Normandy)! 

 Adriatic (Grun.). 



It is not very probable that St. constricta of Ehkbnbbeg represents this species, whatever 

 it may be. 



3. S. (Libellxis) Biblos Cl. (1892). — V. thin and very convex, linear-elliptical with obtuse 

 ends. L. 0,055; B. 0,oi5 mm. Central pores approximate. Central nodule transversely dilated 

 into a narrow stauros. Terminal nodules distant from the ends of the valve. Striae about 30 in 

 0,01 mm. composed of fine puncta somewhat less close, forming undulating, longitudinal rows. 

 Frustnle quadrate. Zone broad, with numerous longitudinal divisions. — Cl. Diatomiste I p. 77 

 PL XII f. 9, 10. 



Marine (pelagic): Barbados! 



This species is of interest as it has a very complex connecting zone and at the same time 

 a well developed stauros. The former characteristic as well as the sculpture of the valve and the 

 distant terminal nodules, prove that it is nearly akin to N. rJiomhica. The latter characteristic 

 shews an affinity to Stauroneis salina. 



4. S. (Libellus) africana Cl. (1881). — V. lanceolate, with subacute ends, convex. L. 0,0 5 

 to 0,06; B. 0,01 to 0,013 mm. Stauros narrow, pervious. Striae 23 in 0,oi mm. transverse. Con- 

 necting zone with faint longitudinal divisions. — Cl. N. P. I), p. 15 PL III f 42. 



Brackish water: South Africa! Ceylon (Weissflog Coll.)! 



Var. acuminata Grun. — V. acuminate. Striae 23 in 0,oi mm. GtRUn. in V. H. T. N:o 137. 

 Marine: Norfolk. 



This species is intermediate between S. constricta and S. salina, having the fine striae of the 

 former and the form of the latter. It is more silicious than S. constricta. 



5. S. salina W. Sm. (1853). — V. lanceolate, witj^ subacute ends. L. 0,o5 to 0,o8; B. 0,012 

 to 0.014 mm. Axial area indistinct. Stauros narrow, slightly dilated towards the margins, pervious. 

 Striae 17 to 18 in 0,oi mm. transverse, finely punctate. — W. Sm. B. D. I p. 60 PL XIX f. 188. 

 V. H. Syn. p. 68 PL X f. 16. Lagst. Boh. D. p. 47 f. 5. 



Marine: North Sea! Mediterranean Sea (Balearic Islands)! Black Sea (Sebastopol) ! 

 Var.? latior Dannf. (1882). — V. broadly lanceolate, with rostrate ends. Striae? — Dannf. 

 Bait. D. p. 32 PL III f. 21. 



Brackish water: Baltic, Bay of Finland (Dannf.). 



6. S. Grregorii Ralfs (1861). — V. lanceolate, gradually tapering from the middle to the 

 obtuse ends. L. 0,05 to 0,i; B. 0,oi to 0,oi.3 mm. Stauros broad, pervious. Striae 16 to 20 in 



K. Sv. Vet. Akad. Handl. Band 26. N:o 2. 19 



