136 p. T. CLEVE, SYNOPSliS OF NAVICULOID DIATOMS. 



verse central area. Striae 9 in 0,oi mm., radiate throughout, coarsely punctate; puncta 12 in 0,oi 

 mm. — Pant. Ill PL XXIII f. 340. 



Habitat:? Mocsar. (Pant.). 



This form resembles N. amphibola or N. Placentula. Unknown to the author. 



Naviculse Bacillares Cl. 



Valve linear to elliptical, usually with broad and rounded ends. Median line straight, en 

 closed by siliceous thickenings. Terminal nodules incrassate. Axial area usually narrow or in- 

 distinct; central area very small. Structure: fine transverse striae, more distant in the middle than 

 elsewhere, slightly radiate througbout and curved, very finely punctate. Connecting zone simple. 



This section comprises forms, which are nearly akin to the N. mesoleice, and it would perhaps 

 be more natural to include in this group N. Pupula and N. hacilliformis, which are closely con- 

 nected with N. Pseudobacillum. On the other hand, the nature of the strise, which are more 

 distant in the middle, indicates a relationship to the section N. decipientes. In the section Bacillares 

 I have included a form, which in some respects is aberrant from the rest, viz. N. americana, which 

 has a broad, axial area and almost equidistant strige. Nevertheless, this form is connected by N_ 

 Lambda with N. Bacillum, and I think it better to place it in this group rather than in the 

 section iV. mesoleice, with which it has still less affinity, or to form a separate group for this single 

 species as Van Hburck has done in his synopsis. 



Artificial hey. 



^ ( Axial area broad . .... , . ■ N. americana Ehb. 



( — — narrow or indistinct ... . . . . . . . 2. 



Central and terminal areas with stigmas . . N. trinotata Pant. 



— — — — without — . . . 3. 



., j Terminal nodules laterally expanded . . . N. Pseudobacillum Grun. 



'''■ \ - -not - - . 4. 



{ 



. / Length 0,06 to 0,i mm. 

 \ — 0,05.') or less . 

 Valve linear . . 



— elliptical 



Terminal fissures comma-like 



»■{■ 



j Termir 



5. 



6. 



. N. Lambda Cl. 



N. Riojas Cl. 



N. subhamulata Gbun. 



not prolonged . . .... ]S[. Bacillum Gbtin. 



1. N. americana Ehb. (1843). — V. broad, linear, with rounded ends. L. 0,o55 to 0,i; 

 B. 0,014 to 0,017 mm. Central nodule strong, with one or two pore-like puncta. Axial and 

 central areas uniting in a very broad space, somewhat dilated in the middle. Strise 16 in 0,oi mm., 

 of equal length, parallel in the middle, radiate in the ends. — Ehb. Am. p. 129 M. G. II: 2, f. 16. 

 V. H. Syn. p. 105 PL XII f 37. N. am. var. bacillaris HfeiB. a. PfinAG. D. d'Auvergne p. 116 

 PL IV f. 13. N. am. var. minor H^rib. a. Perag. 1. c. f. 12 (1893). 



Fresh water: Sweden (Lake Rosslangen in Calmar Ian)! Finland (Abo)! Belgium (V. H.), 

 Australian Alps (Riewa Lagoons)! America (Crane Pond, Boxford, Mass. etc.)! 



This species is very characteristic and not to be mistaken for any other. It is widely 

 distributed, but seems to be rare everywhere. 



2. N. Lambda Cl. N. Sp. — V. linear slightly constricted in the middle, with broad, 

 rounded ends. L. 0,05 to 0,i; B. 0,oi6 ram. Terminal fissures straight in the thick nodules. Axial 

 area narrow but distinct, linear; central area small orbicular. Striae 13 (middle) to 20 (ends) in 

 0,01 mm. divergent in the middle, parallel at the ends, distinctly but finely punctate. — PL V f. 19. 



Fresh water: Demerara Hiver! 



