38 



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



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

 sidered as a series of forms starting from the same point as the Lyrataj, biit 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. Sch a arschniidtii. 



N. fluitans. 



N. abrupt a. 



Iiiterraediate. 



N. carinifera. 

 N. concilians. 



Puiictatae. 



N. scandinavica. 



N. diffusa. 



N. trans fug a. 



N. transfuga var. Neupaueri. 



N. granulata. 



There seems also to be some connection between the Punctatse and the Lineolatse. 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 Punctata}, 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 MicrostictfE the connection is less evident, the forms of that section generally 

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

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



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

 strige alternately longer and shorter, but they have a finer punctation and the stria; are closer 

 towards the ends. 



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

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



Artificial key. 



.. j Valve symmetrical 3. 



I — asymmetrical 2. 



j Ends broad N. Grundleri, Cl. a. Grun. 



\ Ends acute • N. Lunula Cl. 



„ ( Strise of equal length 18. 



' \ — — unequal — (at least in the middle) 4. 



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



4. -1 — rostrate 5. 



— not cuneate or rostrate 9. 



Striae 8 to 9 in 0,oi mm 6. 



0. < — 12 — — 7. 



— IG — — 8. 



. J Terminal fissures in the same directions N. humerosa Breb. 



"I — — — contrary — N. Ali)ha Cl. 



„ j L. 0,03 mm N. Delta Cl. 



'■ \L. 0,07 mm iV. Zi Cl. 



j L. about U,04 mm N. jmsilla W. Sm. 



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



„ J Valve elliptical 10. 



\ — lanceolate 14. 



.,„ j Puncta elongated N. Maeandrina Cl. 



' \ — round 11. 



...J j Length about 0,03 mm 12. 



■ \ — — 0,0 7 mm 13. 



..jj j Median stri® more coarsely punctate than the others N. scintillans A. S. 



■ I — — not — — — — N. scufelloides W. Sm. 



., o j "Without central area N. neogradensis Pant. 



\ With — — . ■ N. algida Grun. 



