108 X^ T. CLEVE, SYNOPSIS OF THE NAVICULOin UIATOMS. 



Centi-al pores of the median line approximate. Striicture: small puncta arraujred in parallel, trans- 

 verse and longitudinal i'ows, crossiiig each other at a right angle. Axial and central areas small 

 or indistinct. Connecting zoiie not complex. 



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

 and the structure of the valve, but the longitndinal strife of the valve are less distinct in Fusi- 

 formes. Some forms of Orthostichfe seem to be connected with Gyrosignia. The smaller forms of 

 this section, Nav. gregaria to i\^ niicrorliynclms, have no distinct longitudinal stria», bnt have been 

 placed here, as they seem to be connected with Nav. Jtalophila.- On the other hand they appear to 

 come near to Nav. cryptocephala of the section Lineolataj. Some species have transversely dilated 

 central nodules, and have been considered as belonging to the genus Stauroncis, but there is verv 

 little resemblance between there forms and the true Staiiroiieis (division of Microstig)naticcB), in the 

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



Artificiell Jcey. 



^ ( Central notlule dilated into a stauros 11. 



■ \ — — not — — 2. 



„ ) Longitudinal stria; indistinct -. . .iVv.- i . 'i: i;'; i;'j. . w j! l .-l) ■. .■'. . 3. 



" \ — — distinct 6. 



„ I StriiB nninterrupted in the middle 4. 



1 — inteiTuiJted .... . 5. 



, I Ends acute .....'..■ N. microrhynchus Gru>-. 



\ — rostrate to capitate N. gregaria Donk. 



J Strije crossed lij' a longitudinal depression N. Wankarem(e Cl. 



\ — not — — — N. Kryokonites Cl. 



j Terminal striae convergent JN^. holophila Geun. 



■ \ — — not — 7. 



j Valve broadly linear, with broad ends X. portomontana Cl. 



\ — linear or lanceolate, navrowed towards the end 8. 



f Transverse strise more distant than the longitudinal N. cnspidata KtJTZ. 



8. — — closer — — — '. . . N. Perrottetii Gefn. 



I — — equidistant with — 9. 



„ J Ends acute : iV. vitrea Cl. 



1 — rounded u i . ,-.i 10. 



„ I Striaä 15 in 0,oi mm X KjcUmanii Cl. 



I — closer — X. 0'Mcarn Gkun. 



( Stauros short X. balearica Cl. 



11- ■! — reaching halfway to the margin X. quarnerensis Gkun. 



( — pervions — — — 12. 



. ..g ) Valve rhombic-lanceolate X. Stodderi Geeenl. 



\ — linear or linear-lanceolate 13. 



..„ I Longitudinal stri» more distant than the transverse X. snlcata Cl. 



\ — — closer — — — 14. 



... ) Transverse stris 12 in 0,01 mm X. crncigera W. Sm. 



'I — — about 26 in 0,0 1 mm X. Spicula Hickxe. 



1. N. gregaria Donk. (1861). — V. lanceolate, with rostrate-capitate ends. L. O.uui to 

 0,0:35; B. 0,005 to 0,009 mm. Transverse strife 16 to 22 in 0, 01 mm. Longitudinal stri;e indis- 

 tinct. — Donk. M. J. I p. 10 Pl. I f. 10. B. D. p. 43 Pl. VI f 13. V. H.' Syn. p. 85 Pl. Mil 

 f. 12—15. Nav. cryptoccphuJa W. Sm. B. D. Pl. XVII f 155. Pedicino Ischiall f. 9—11. Nav. 

 lanceolata W. Sm. B. D. p. 46 Pl. XXXI f. 272? Nac. veneta ScuuM. P. D. II X. Pl. II f. 30. 

 .Vffli'. Granum Avence Schum. P. D. N. II p. 56 Pl. II f. 36 (1867)? 



Brackish water: Sweden (Bohuslän)! England! Saxony (Salines Dllrrenberg)! Belgium ( V. H.) 

 Prance! South Africa! Argentina! 



I 



