108 p. T. CLEVE, SYNOPSIS OF THE NAVICULOII) DIATOMS. 



Central pores of the median line approximate. Structure: small puncta arranged in parallel, trans- 

 verse and longitudinal rows, crossing each other at a right angle. Axial and central areas small 

 or indistinct. Connecting zone not complex. 



This group is closely related to the Section Fusiformes, by the approximate central pores 

 and the structure of the valve, but the longitudinal striic of the valve are less distinct in Fusi- 

 formes. Some forms of OrthostichcB seem to be connected with Gyrosigma. The smaller forms of 

 this section, Nav. grefjaria to N. microrhynchus, have no distinct longitudinal strice., but have been 

 placed here, as they seem to be connected vi^ith Xav. halophila. On the other hand they appear to 

 come near to Xav. crypfocephala of the section Lineolataj. Some species have transversely dilated 

 central nodules, and have been considered as belonging to tlie genus Sfauroneis, but there is very 

 little resemblance between there forms and the true Stauroncis (division of Microstigniaticce), in the 

 structure of the valve, which is the same as in other orthostichiu. 



Artificial Jcey. 



^ J Central nodule dilated into a stauros 11. 



\ — — not — — 2. 



„ j Longitudinal striie indistinct i]. 



^' \ — — distinct (j. 



) Stria; uninterrupted in the middle 4. 



\ — interrupted 5. 



, I Ends acute N. microrhynchus Grun. 



I — rostrate to capitate N. greyaria Donk. 



J Strise crossed by a longitudinal depression N. WankaremcB Cl. 



'I — not — — • — N. Kryokonites Cl. 



) Terminal strice convergent N. holophila Gsun. 



\ - - not - 7. 



^ j Valve broadly linear, with broad ends X portoiiKintana Cl. 



^ — linear or lanceolate, narrowed toward.s the end 8. 



{Transverse striae more distant than the longitudinal N. cuspidata Kutz. 

 — — closer — — ■ — iV. Perrottetii Geun. 

 — equidistant with — • 9. 



„ j Ends acute N. vitrea Cl. 



' \ — rounded 10. 



„ ) Strife 15 in 0,oi mm N. Kjellmanii Cl. 



\ — closer — N. O'Mearii Geun. 



i Stauros short N. balearica Cl. 



11. ■! — reaching halfway to the margin N. quarnerensis Grun. 



\ — pervious — — — 12. 



Valve rhombic-lanceolate N. Stoddcri Greenl. 



12. 1^: 



12. , 



I — linear or linear-lanceolate 13. 



_.,, I Longitudinal strise more distant than the transverse N. sulcata Cl. 



' ^ — — closer — — — 14. 



... j Transverse striae 12 in 0,oi mm N. crucigera W. Sm. 



' I — — about 26 in 0,oi mm N. Spicula Hickie. 



1. N. gregai'ia Donk. (18G1). — V. lanceolate, with rostrate-capitate ends. L. 0,oi.'j to 

 0,();55; B. (),()()r, to 0,oo9 mm. Transverse stripe 16 to 22 in 0,oi mm. Longitudinal striae indis- 

 tinct. — Donk. M. J. 1 p. 10 PI. I f. 10. B. D. p. 43 PI. VI f. 13. V. H. Syn. p. Hb PI. Vlll 

 f. 12—15. Nav. cryptoccphala AV. Sm. B. D. PI. XVII f. 155. Pedicino Ischia "li f. 9—11: Xar. 

 lanceolata W. Sm. B. D. p. 4(5 PI. XXXI f. 272? Nav. veneta ScuuM. P. D. II N. PI. II f. 30. 

 Nav. Grail am Avence ScnuM. P. 1). N. II p. 56 PI. II f. 36 (1867)? 



Brackish water: Sweden (Bohuslan)! England! Saxony (Salines Diirrenberg)! Belgium (V. H.) 

 France! South Africa! Argentina! 



