136 P. T. CLEVE, SYNOPSIS OF NAVICULOll) DIATOMS. 



verse central area. Strite 9 in 0,oi mm., radiate tliroughout, coarsely punctate; puncta 12 in 0,iji 

 mm. — Pant. III Pl. XXIII f. 340. 



Habitat:? Mocsår. (Pant.). 



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



Naviculse Bacillares Cl. 



Valve linear to elliptical, nsually with broad and ronnded ends. Median line straight, en 

 closed by siliceous tlnckenings. Terminal nodnles incrassate. Axia] area nsually narrow or in- 

 distinct; central area very small. Structure: fine transvejse stria;, 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 K. mesoleios, and it -n-ould perhaps 

 be more natural to include in this group JS^. Piqjuhi and -.T. bacilliformis, which are closeh" con- 

 nected with N. Psendohacillum. On the otiier hand, the nature of the strise, which are more 

 distant in the middle, indicates a relationship to the section K. clecipientes. In the section Bacillares 

 I have included a form, which in some respects is aberrant from the rest, viz. -A^ americona, which 

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

 Lamhda with iV. Badllum, and I think it better to place it in this group rather than in the 

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

 species as Van Heurck has done in his synopsis. 



Artificial key. 



Axial area broad N. americana Ehb. 



— — narrow or inclistinet 2. 



^, ( Central and terminal areas with stigmas N. trinotafa Pant. 



— — — — without — 3. 



Terminal nodules laterally expanded N. Pseudobacilhim Gel-n. 



— — not — — 4. 



Length 0,oc to 0,1 mm 5. 



— 0,055 or less 6. 



Valve linear N. Lambda Cl. 



— elliptical K. Biojoe Cl. 



. Terminal fissures comma-like . N. suhhamulata Grun. 



— not prolonged N. Bacillum Grun. 



M 



{' 



1. N. Jimericanii Ehb. (1843). — V. broad, linear, with rounded ends. L. O,o.'j.-i to O, 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. Strite 16 in O.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. hacillaris Hérib. a. Pérag. D. d'Anvergiie p. 116 

 Pl. IV f. 13. iV. am. var. minor Hérib. a. Perag. 1. c. f. 12 (1893). 



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

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



This species is very characteri.stic 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 slightl}' constricted in the middle. with broad, 

 rounded ends. L. 0,05 to 0,i; B. 0,0 i 6 mm. Terminal fissures straight in the thick nodules. Axial 

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

 0,0 1 mm. divergent in the middle, parallel at the ends, distinctly but tinely punctate. — Pl. V f. 19. 



Fresh water: Demerara River! 



