86 P. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



This species is of very frequent occiirence 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. paulensis 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. Strise 14 to 15 in 0, 01 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:ii Paolo)! 



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

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

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

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



Fresh water: Sweden (Hosslängen in Kalmar län)! Finland! Bengal! 



Var. leptostauron Cl. (1891). — L. 0,075 to 0, 01; B. 0, 013 mm. Strise 10 in 0, 01 mm., inter- 

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



Fresh water: Sweden (Stensele Lappmark, Rosslängen in Kalmar län, Öjasjö in Blekinge)! 

 Finland (Tavastland)! Scotland (Ordie Dept.)! Grermany (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. Striaj 10 in 0, 01 mm. 



Fresh water: Demerara River! 



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

 the ends. L. 0,o32 to O, 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, 15 to O.is; B. 0, 02 mm. Strise 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 c/enuina — L. 0,i; B. 0,oi2 mm. Stritc 10 to 12 in 0,oi mm. — Frustulia acrosphceria 

 Bréb. Considér. p. 19. Nav. acrosph. KtJTZ Bac. p. 97 Pl. V f. 2. Donk. Br. D. p. 72 Pl. XII 

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



Fresh water: Sweden (Rosslängen in Kalmar län)! Finland (Savolaks)! Scotland (Atl.), 

 Bengal! Illinois! Brazil (Caldas)! Ecuador! 



Forma minor. — L. 0, 035 to 0,07; B. 0,oo8 to 0, 01 mm. Strise 13 to 14 in 0, 01 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, 0,012 

 mm. Striaj 12 in 0, 01 mm. 



Fresh water: Waltham Mass.! 



Var. undulata Cl, — V. with threo slight inflations. L. 0, 1 1; B. 0,012 mm. Strise 12 in 0, 01 mm. 



Fresh water: Sweden (Lake Rosslängen in Kalmar län)! 



Var. Icevis Cl. — L. 0,o83; B. 0,oi7 mm. Area smooth. Stria; 8 to 12 in 0,01 mm. — 

 A. S. Atl. XLIII f. 18. 



Fresh water: New Zealand! Australia (Blue Monntain.s)! 



45. P. singnlaris A. S. (1876). — V. giblions in tlie middle, with cunpate and oapitate 

 ends. L. O, iun; B. 0,01',) mm. Median line stråight, with approximate central poi'es and conima- 



