38 P. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



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

 sidered as a series of forms står ting from the same point as the Lyratse, bnt rather as a parallel 

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



Lyrate. Intermediate. Punctatae. 



-ZV. Lyra. N. carinifera. N. scandinavica. 



N. connectens. N. concilians. N. diffusa. 



N. Schaarsckmidtii. N. transfuga. 



N. fluitans. N. transfuga var. JSfeupaueri. 



N. abrupta. ■ N. granulata. 



There seems also to be some connection between the Punctatse and the Lineolatee. Thus 

 N. amphibola is no doubt akin to JSf. 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 vrhich are some coarsely punc- 

 tate forms. 



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

 having the puncta closer than the striee. In the Mesoleiee there are also some small forms, 

 which might be placed in this section, for instance N. fiivalis 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 strise 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 Jcey. 



{ 

 { 



Valve symmetrioal 3. 



— asymmetrioal 2. 



Ends broad ^ . . . . N. Grundleri Cl. a. Geun. 



Ends acute N. Lunula Cl. 



/ Striae of equal length 18. 



\ — — uneqnal — (at least in tlie middle) 4. 



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



— rostrate 5. 



— not cuneate or rostrate 9. 



{Strise 8 to 9 in 0,oi mm 6. 



— 12 — — 7. 

 — 16 — — S. 



I Terminal fissures in the same directions N. humerosa Bréb. 



1 — — — • contrary — N. Alpha Cl. 



( L. 0,03 mm N. Delta Cl. 



\ L. 0,07 mm iV. Zi Cl. 



/ L. abont 0,04 mm N. imsilla W. Sm. 



I L, about 0,09 mm N. Délawarensis Grun. 



g J Valve ellijitical 10. 



\ — lanceolate 14. 



.j, j Puncta elongated N. Maeandrina Cl. 



1 — round 11. 



-.- / Length abont 0,03 mm IS. 



' \ — — 0,0 7 mm 13. 



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



I — — not — — — — jV. sciitelloidcs W. Sm. 



y, ) Withont central area N. neogradcnsin Pant. 



I With — — . • N- algida Grun. 



