86 p. T. CLEVK, SYNOPSIS OF THE NAVICULOID DIATOMS. 



This species is of very frequent occurence and very variable, especially as to the breadth 

 of the axial area, which sometimes becomes very broad as in the form named by A. S. Nav. instabilis. 



42. P. panlensis Grun. Ms. — V. linear, slightly narrowed to the obtuse, rounded ends. 

 L. 0,065 to 0,14; B. 0,011 to 0,014 mm. Median line filiform, with approximate central pores and 

 slightly curved, elongate, terminal fissures. Axial area wide, about a third of the breadth of the 

 valve, linear. Striae 14 to 15 in 0,oi mm., almost transverse to the ends. — A. S. Atl. XLIII 

 f. 7, 8, 9 (without name). Icon. n. PL I f. 20. 



Fresh water: America (Greenland, "White Mountains, Cherryfield, Monmouth, Ducks Pond, 

 Maine, Sierra Nevada, Demerara River, Brazil, Caldas, S:n Paolo)! 



43. P. brevicostata Cl. (1891). — V. linear, with parallel margins and broad, rounded 

 ends. L. 0,i to 0,12; B, 0,oi6 mm. Median line almost filiform. Terminal fissures comma-like. 

 Area very broad, irregularly lanceolate. Strise 8 to 9 in 0,oi mm. parallel throughout. — Nav. 

 heniiptera A. S. Atl. XLIII f 26, 27. Finn, brevicostata Cl. D. of Finl. p. 25 PI. I f. 5. 



Fresh water: Sweden (Eosslangen in Kalmar Ian)! Finland! Bengal! 



Var. leptostauron Cl. (1891). — L. 0,o7ft to 0,oi; B. 0,oi3 mm. Striee 10 in 0,oi mm., inter- 

 rupted in the middle. A. S. Atl. XLIII f 25 (without name). — D. of Finl. p. 25. 



Fresh water: Sweden (Stensele Lappmark, Rosslangen in Kalmar Ian, Ojasjo in Blekinge)! 

 Finland (Tavastland) ! Scotland (Ordie Dept.)! Germany (Laacher See, Atl.), France (Lac de Ge- 

 rardmer, Vosges)! 



Var. Demerarce Cl. — V. linear, attenuated towards the subcuneate ends. L. 0,07; B. 0,oi 

 mm. Area about a third as broad as the valve. Central area a transverse fascia. Strise 10 in 0,oi mm. 



Fresh water: Demerara River! 



44. P. acrosphaeria Br^b. (1838). — V. linear, more or less gibbous in the middle and at 

 the ends. L. 0,032 to 0, is; B. 0,oo8 to 0,02 mm. Median line filiform, its central pores approxi- 

 mate and its terminal fissures semicircular. Axial area about a third as broad as the valve, 

 finely punctate. Strise 9 to 14 in 0,oi mm. parallel, or slightly radiate at the ends. 



Forma maxima. — L. 0,i5 to 0,i8; B. 0,02 mm. Striae 9 in 0,oi mm. — Nao. acrosph. var. 

 sandvicensis A. S. Atl. XLIII f. 14, 15. 



Fresh water: Java (eatable earth)! New Zealand! Sandwich Islands (Atl.). 



Forma genuina — L. 0,i ; B. 0,oi2 mm. Strise 10 to 12 in 0,oi mm. — Frustulia acrosphceria 

 BrSb. Consider, p. 19. Nav. acrosph. KtJTZ Bac. p. 97 PI. V f 2. Donk. Br. D. p. 72 PI. XII 

 f. 2. W. Sm. B. D. XIX f 183. A. S. Atl. XLIII i. 16 (22?). 



Fresh water: Sweden (Rosslangen in Kalmar Ian)! Finland (Savolaks)! Scotland (Atl.), 

 Bengal! Illinois! Brazil (Caldas)! Ecuador! 



Forma minor. — L. 0,03,'5 to 0,07; B. 0,oo8 to O.oi mm. Strise 13 to 14 in 0,oi mm. — 

 A. S. Atl. XLIII f 23. 



Fresh water: Bengal! Australia (Blue Mountains)! Pensacola (Atl.), California! 



Var. turgidula Grun. Ms. — V. strongly gibbous in the middle. L. 0,04 8 to 0,07; B, 0,oi2 

 mm. Strise 12 in 0,oi mm. 



Fresh water: "Waltham Mass.! 



Var. undulata Cl, — V. with three slight inflations. L. 0,i 1 ; B. 0,oi 2 mm. Strise 12 in 0,oi mm. 



Fresh water: Sweden (Lake Rosslangen in Kalmar Ian)! 



Var. Icevis Cl. — L. 0,08,<i; B. 0,oi7 mm. Area smooth. Strise 8 to 12 in 0,oi mm. — 

 A. S. Atl. XLIII f 18. 



Fresh water: New Zealand! Australia (Blue Mountains)! 



45. P. Singularis A. S. (1876). — V. gibbous in the middle, with cuneate and capitate 

 ends. L. 0,i06; B. 0,oi9 mm. Median line straight, with approximate central pores and comma- 



