136 P. T. CLEVE, SYNOPSIS OF NAVICULOID DIATOMS. 



verse central area. StritE 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. (imphihola or N. VJacentula. 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 strict;, more distant in the middle than 

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



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

 be more natural to include in this group N. Fttpuhi and X. bacilliformis, which are closely con- 

 nected with N. P.sendnhaciUiim. On the other hand, the nature of the strite, 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 stria?,. Nevertheless, this form is connected by N_ 

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

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

 species as Van Heurck has done in his synop.sis. 



Artificial hey. 



I Axial nrea l)road N. americana Ehb. 



' \ — — narrow or imlistinct 2. 



jj J Central ami terminal areas with stigraas N. trinotafa Pant. 



' \ — — — — without. — 3. 



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



'■ \ — — not — — 4. 



, j Lenicth O.on to 0,i mm 5. 



\ — 0,o,').') or less 6. 



Valve linear N- Lambda Cl. 



— elliptical N. Rinjw Cl. 



Terminal fissures comma-like N. mihharnulata Grun. 



not prolonged K. Bacillnm Grun. 



,. I Termi 



1. N. nmericaiiii Ehb. (1843). — V. broad, linear, with rounded ends. L. 0,o.-)5 to 0, i; 

 B. 0,0 14 to 0,0 17 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. Stri;e 1(5 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 PI. XII f. 37. N. urn. var. hacillarif^ H^rib. a. Perag. D. d'Auvergne p. 116 

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



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

 Australian Alps (Riewa Lagoons)! America (Crane Pond, Boxfoi-d, Mass. etc.)! 



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

 distributed, but seems to be rare everywhere. 



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

 rounded ends. L. OjO.'j to 0, i ; B. O,oifi mm. Terminal fissures straight in the thick nodules. Axial 

 area narrow but distinct, linear; central area small orlncular. Strict' 13 (middle) to 20 (ends) in 

 0,0 1 mm. divergent in llie middle, parallel at the ends, distinctly but finely punctate. — PI. V f. 19. 



Fresh watei': Deraerara liiver! 



