170 P. T. CLEVE, SYNOPSIS OF THE NAVICULOIU DIATOM.S. 



terminal iiodules at some distance from the ends. Axial area narrow, central area small, orbiciilar. 

 Strise 14 to 15 in 0,(ii 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 2<J8. 



Fresli water (alpine regions): (xreenland! Iceland! Norway (Dovre, Romsdalen)! Sweden 

 (Pauträsk, Wilhelmina socken)! 



C. norvegica is nearly akin to C. gracilis and diifers prineipally by its more linear form 

 and broad, rounded ends. 



44. 0. incertii Grun. (1878). — V. linear, slightly asymmetrical, with broad, obtuse euds, 

 slightly arcnate dorsal margin and almost straight ventral. L. 0,o4 to (),ot;B. 0,ou9 mm. Median 

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

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

 var. mccrta Griux. Cl. M. D. N:o 96. Cl. I), fr. Grönl. och Argent. p. 13 Pl. XVI f. 12. G. suh- 

 cequalis var. inccrta Grun. in V. H. T. N:o oO. 



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

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



Var. naviculacca Grun. (1879). — With somewhat wider axial area and finer strise, about 

 18 in 0,0 1 mm. — C. {Fi^ciculu.i var.) naviculacea Grun. in Cl. M. D. N:o 272. Cl. D. fr. Grönl. 

 och Argentina p. 13 Pl. XVI f. 11. 



Fresh water: Greenland! Norway (Do^•re)! Sweden (Lapland to Jämtland)! Finland (Russian 

 Lapland) ! 



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

 slightly convex ventral margin, and broad, obtuse, or almost truncate ends. L. 0,o3 to 0,045; B. 0,ooG 

 to 0,0 11 mm. Median line straight, near to the ventral margin, broad (oblique). Axial area 

 narrow, not, or slightly, dilated in the middle. Strise 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. U. II p. 84. 

 Cymh. oUusa Greg. M. J. IV Pl. I f. 19 (1856). A^ H. Syn. p. 61 Pl. Ill f. 1 a. A. S. Atl. IX 

 f. 41 to 45; LXXI f. 72? Gyml. suhcequalis Grun. V. H. Syn. Pl. III f. 2, 4 Suppl. Af. 1 (1880). 



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

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



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

 0,0 1 mm. — Cymh. suhccquali.s var. florentina Grun. in V. H. Syn. Pl. III f. 3. 



Fresb water: S:ta Flora, foss. (Grun.). 



Var. diminida Grun. — L. 0,oi5; B. 0,oo4 mm. Strise 12 to 15 in 0,oi mm. — Cymh. ohtiisa 

 var. diminuta Grun. in V. H. T. ]SI":o 129. 



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



C. (cqnaJis W. Sm. is usually believed to denote the same species as C. angiisfafa, but as 

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

 this is a mistake, and that Smith meant the form described above as C. tequalis. Gregory's figui'e 

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

 Between Cymh. suhcequalis Grun. and Cymh. ohtusa Greg. as represented in Van Heurck's Synopsis 

 I am unable to discover any specific distinction. As limited here Cymh. eequalis is a common 

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

 tant than the others and radiate. 



46. C. siiuiata Greg. (1856). — V. linear, slighth' asymmetrical, frequently gibbous in the 

 middle on tbe ventral side, with broad, obtuse ends. L. 0,oi2 to 0,o2g; B. 0,oo4 to O.oo.^, mm. 

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

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

 f. 8 (1880). Gomplionema asymmetricum GuTW. p. 28 Pl. I f. 24? 



