38 



p. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



The division, comprising forms with the median strise of equal length, is not to be con- 

 sidered as a series of forms starting from the same point as the Lyratse, but rather as a parallel 

 row of allied forms. For instance the following forms may be regarded as nearly connected: 



Lyrate. 



N. Lyra. 



N. connectens. 



N. Schaarsehinidtii. 



N. fluitans. 



N. ahrupta. 



Intermediate. 



N. carinifera. 

 N. concilians. 



Punctatae. 



N. scandinavica. 



N. diffusa. 



N. transfuga. 



JV. transfuga var. NeupaUeri: 



N. granulata. 



There seems also to be some connection between the Punctatae and the Lineolatae. Thus 

 N. amphihola is no doubt akin to N. Gastrum. Several species of Cymbella, which have distant 

 puncta (C aspera, C. mexicana etc.) seems also to be related to Punctatae, but they have broader 

 axial areas. The same is also the case with the Entoleise, among which are some coarsely punc- 

 tate forms. 



With the Microstictse the connection is less evident, the forms of that section generally 

 having the puncta closer than the strise. In the Mesoleise there are also some small forms, 

 which might be placed in this section, for instance N. nivalis and others. 



The HeterostichEe are apparently akin to the forms of the division, which have the median 

 strise alternately longer and shorter, but they have a finer punctation and the striae are closer 

 towards the ends. 



Most forms of the section Punctatae are marine, a few only living in fresh water. Some 

 are decidedly inhabitants of brackish water. They occur in all zones and seas. 



Artificial hey. 



6. 



7. 



8. 



9. 

 10. 

 11. 

 12. 

 13. 



j Valve symmetrical 



\ — asymmetrical 



j Ends broad 



\ Ends acute .... 



f Stris of equal length 



\ — — unequal — (at least in the middle) 



f Ends euneate 



< — rostrate . 



( — not euneate or rostrate 

 Striae 8 to 9 in 0,01 mm ., 



— 12 — — 



— 16 — — 



Terminal fissures in the same directions . . 



— — — contrary — . . 



L. 0,03 mm 



L. 0,07 mm 



3. 



2. 



. N. Grundleri Cl. a. Gk0n. 



N. Lunula Cl. 



18. 



... 4. 



. N. Eta Cl. (N. humerosa var.). 

 5. 



9. 

 6. 



7. 



N. humerosa Bej^b. 



. . N. Alpha Cl. 



. . N. Delta Cl. 

 iV. Zi Cl. 



f L. about 0,04 mm N. pusilla W. Sm. 



\L. about 0,09 mm N. Delawarensis Geun. 



( Valve elliptical ... . . . . . . ... 10. 



\ — lanceolate ... . 14. 



( Puncta elongated N. Maeandrina Cl. 



\ — round 11. 



f Length about 0,03 mm 13. 



\ — — 0,07 mm 13. 



{Median strise more coarsely punctate than the others N. scintillans A. S. 

 — — not — — — — N. scutelloides W. Sm. 



( Without central area . N. neogradensis Pant. 



\ With — — iV. algida Gbttn. 



