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



terminal nodules at some distance from the ends. Axial area narrow, central area small, orbicular. 

 Striae 14 to 15 in 0,oi mm. slightly radiate in the middle, where they are more distant, parallel 

 at the ends. — Grun. in A. S. Atl. X f. 41. Cl. M. D. N:o 268. 



Fresh water (alpine regions): Greenland! Iceland! Norway (Dovre, Romsdalen)! Sweden 

 (Paiitrask, Wilhelmina socken)! 



C. norvegica is nearly akin to C. gracilis and differs principally by its more linear form 

 and broad, rounded ends. 



44. C. incerta Grun. (1878). — V. linear, slightly asymmetrical, with broad, obtuse ends, 

 slightly arcuate dorsal margin and almost straight ventral. L. 0,04 to 0,o7; B. 0,oo9 mm. Median 

 line almost central. Axial area narrow, not dilated in the middle. Striae 14 to 16 in 0,oi mm., 

 equidistant in the middle, where they are parallel, and slightly radiate at the ends. — G. Pisciculus 

 var. incerta Grun. Cl. M. D. N:o 96. Cl. D. fr. Gronl. och Argent, p. 13 PL XVI f. 12. G. sub- 

 cequalis var. incerta Grun. in V. H. T. N:o 30. 



Fresh water, northern or alpine regions: Norway (Dovre, Hammerfest)! Sweden (Lapland)! 

 Finland (Russian Lapland)! Scotland (V. H. T.). 



Var. navicidacea Grdn. (1879). — With somewhat wider axial area and finer striae, about 

 18 in 0,01 mm. — C. {Pisciculus var.) naviculacea Grun. in Cl. M. D. N:o 272. Cl. D. fr. Gronl. 

 och Argentina p. 13 PL XVI f. 11. 



Fresh water: Greenland! Norway (Dovre)! Sweden (Lapland to Jamtland)! Finland (Russian 

 Lapland) ! 



45. C. iequalis W. Sm. (1856). — V. linear-lanceolate, with arcuate dorsal, straight or 

 slightly convex ventral margin, and broad, obtuse, or almost truncate ends. L. 0,03 to 0,o45; B. 0,oo6 

 to 0,011 mm. Median line straight, near to the ventral margin, broad (oblique). Axial area 

 narrow, not, or slightly, dilated in the middle. Striae 11 or 14 (middle) to 14 or 16 (ends) in 0,oi 

 mm., slightly radiate, obscurely punctate; puncta about 16 in 0,oi mm. — "W. Sm. B. D. II p. 84. 

 Cymh. ohtusa Greg. M. J. IV PL I f. 19 (1856). V. H. Syn. p. 61 PL III f. 1 a. A. S. Atl. IX 

 f. 41 to 45; LXXI f. 72? Gymh. subwqualis Grun. V. H. Syn. PL III f. 2, 4 Suppl. A f . 1 (1880). 



Fresh water: Greenland! Iceland! Scotland and England! Sweden (Lapland to Skane, Goth- 

 land)! Norway (Dovre, Stavanger, foss.)! Belgium (V. H.), Saxony! Switzerland! Michigan! 



Var. florentina Grun. (1880). — V. less asymmetrical, almost lanceolate. Striae finer, 15 in 

 0,01 mm. — Gymb. subcequalis var. florentina Grun. in V. H. Syn. PL III f. 3. 



Fresh water: S:ta Fiora, foss. (Grun.). 



Var. diminuta Grun. — L. 0,oi5; B. 0,oo4 mm. Striae 12 to 15 in 0,oi mm. — Gymb. obtusa 

 var. diminuta Gkun. in V. H. T. N:o 129. 



Fresh water: England (V. H. T.). 



C. mqualis W. Sm. is usually believed to denote the same species as G. angustata, but as 

 the ends are described as obtuse and the striae are coarse, 12 in 0,oi mm., it is evident that 

 this is a mistake, and that Smith meant the form described above as G. cequalis. Gresory's figure 

 of Gymh. obtusa is small and not very characteristic, but agrees pretty well with this species. 

 Between Gymb. subcequalis Grun. and Gymb. obtusa Greg, as represented in Van Heurck's Synopsis 

 I am unable to discover any specific distinction. As limited here Gymb. cequalis is a common 

 form, distinguished by its linear form and almost truncate ends. The median striae are more dis- 

 tant than the others and radiate. 



46. C. siituata Greg. (1856). — V. linear, slightly asymmetrical, frequently gibbous in the 

 middle on the ventral side, with broad, obtuse ends. L. 0,oi2 to 0,026; B. 0,oo4 to 0,oo5 mm. 

 Axial area narrow; central area large, on the ventral side reaching to the margin. Striae 9 to 11 

 0,01 mm., almost parallel. — Greg. M. J. IV PL I f. 17. G. abnormis Grun. in V. H. Syn. PL III 

 f. 8 (1880). Gomphonema asymmetricum Gutw. p. 28 PL I f, 24? 



