86 p. T. CLEVE, SYNOPSIS OK THE NAVICULOH) 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. Nov. instahUis. 



42. P. pauleusis (tRUN. Ms. — V. linear, slightly narrowed to the obtuse, rounded ends. 

 L. (),(M).'i 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 PI. I f. 20. 



Fresh water: America (Greenland, White Mountains, ('herryfield, Monmouth, Ducks Pond, 

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



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

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

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

 hemipiera A. S. Atl. XLIII f. 2ii, 27. Finn, hrcvicostata Cl. 1). of Finl. p. 25 PI. I f. 5. 



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



Var. leptostauron Cl. (1891). — L. (),{)ih to 0,oi; B. 0,01;; mm. Striae 10 in 0,01 mm., inter- 

 rupted in the middle. A. S. Atl. XLIII f. 25 (without name). — 1). 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. Demerara 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. Striae 10 in 0,oi mm. 



Fresh water: Demerara River! 



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

 the ends. L. 0,032 to 0,i8; 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. Stria-. 9 to 14 in (),oi mm. parallel, or slightly radiate at the ends. 



Forma maxima. — L. 0, 1.5 to 0,i8; B. 0,0 2 mm. Stria'. 9 in 0,oi mm. — Nav. acro.sph. car. 

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



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



Forma geniiina — L. 0, 1; B. 0,012 mm. Strite 10 to 12 in 0,oi mm. — Frnstulia acrosjihceria 

 Bri5b. Consider, p. 19. Nav. acrosph. KtJTZ Bac. p. 97 PI. V f. 2. Donk. Br. D. p. 72 PL XII 

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



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

 Bengal! Illinois! Brazil (Caldas)! Ecuador! 



Forma minor. — L. 0,o3.') to 0,07; B. 0,008 to O.m mm. Striae 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,o4 8 to 0,07; B, 0,012 

 mm. Striae 12 in 0,oi mm. 



Fresh water: Waltham Mass.! 



Var. tindulata Cl. — V. with three slight inflations. L. 0, 1 1 ; B. 0,012 mm. Stria; 12 in 0,oi mm. 



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



Var. l(Bvis Cl. — L. 0,08,s; B. 0,oi7 mm. Area smooth. Strift 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. (187(i). — V. gibbous in the middle, with cuneate and capitate 

 ends. L. 0, iob; B. 0,0 m mm. Median line straight, with approximate central jiores and ccmima- 



