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



20. P. Hartleyana Grev. (1865). — V. linear, gibbous in the middle and at the ends. 

 L. 0,2 to 0,23; B. 0,033 to 0,045 mm. Median line straight, filiform. Axial area linear, less than 

 1/3 as broad as the valve, in the middle transversely dilated, frequently to a fascia. Strise 8 in 

 0,01 mm. divergent in the middle, convergent at the ends. — T. M. S. vol. XIII Pl. VI f. 30. 



Fresh water: Liberia (Grev.), Demerara River! 



21. P. episcopalis Cl. (1891). — V. linear, with parallel margins and broad rounded ends. 

 L. 0,23 to 0,36; B. 0,035 to 0,04 mm. Median line filiform with eomma-like terminal fissures. 

 Axial area broad, about ','3 of the breadth of the valve, in the middle widened to a transverse 

 fascia. Striae 8 in 0,oi mm., strongly divergent in the middle and convergent at the ends. — 

 P. cardinalis Ehb. M. G. XVIII: i f. 4. P. episcopalis Cl. D. of Finl. p. 27 Pl. I f. 4. 



Fresh water: Sweden (Lake Wenern, Lake Rosslängen in Kalmar län, Öjasjö Dept. in Ble- 

 kinge, interglacial mud from Hernösand)! Finland! Lac Gerardmer, Vosges! Cherryfield, America! 



Var. hrevis Cl. — L. 0,i8; B. 0,038 mm. Striae 6 in 0,oi mm. less radiate. 



Fresh water: New Zealand (Auckland, Witt CoU.)! 



Var. africana Cl. — V. smaller. L. 0,115; B. 0,oi8 mm. Axial area less than a third of 

 the breadth of the valve. , Striee 8 in 0, 01 mm. 



Fresh water, mouth of rivers: Cameroon, Africa! 



P. episcopalis is a very large and beautiful diatom, nearly akin to P. divergens and to 

 P. Hartleyana. 



IV. Distantes. 



Artificial hey. 



\ 



, Valve lanceolate P. alpina W. Sm. 



— raore or less narrow, elliptical Si. 



Very small forms. L. about 0,ni mm P. Balfouriana Gbun. 



Length 0,os to 0,1 mm. and more 3. 



0,1 mm. and more P. lata Beéb. 



less than 0,1 mm 4. 



Strise 5 to 6 in 0,01 mm P. borealis Ehb. 



— 8 in 0,01 mm P. intermedia Lägst. 





22. P. intermedia Lägst. (1873). — V. linear-elliptical, with rounded ends. L. 0,oi8 to 

 0,042; B. 0,06 to 0,08 mm. Axial area narrow; central a transverse fascia. Strise radiate at the 

 ends, 8 in 0,oi mm. — Nav. int. Lägst. Spetsb. D. 23 Pl. I f. 3. 



Fresh water: Spitsbergen (Lägst.), Beeren Eiland (Lägst.), Australia (Blne Mountains)! 

 This form seems, according to Lagerstedt, to graduate into P. borealis and P. Brébissonii. 



23. P. Balfouriana Grun. Ms. — V. elliptical. L. 0,oo8 to 0,oi; B. 0,ooj mm. Area wide. 

 Strittt distant, 10 in 0,oi mm. — Pl. I f. 18. 



Fresh water: Scotland (Grun.), North Iceland! 



24. P. borealis Ehb. (1843). — V. linear-elliptical, with rour.ded or subtruncate ends. L. 

 0,03 to 0,06; B. 0,007 to 0,oo8 mm. Median line with approximate central pores and hook-shaped 

 terminal fissures. Area narrow Striaä parallel, 5 to 6 in 0,oi mm. — Am. Pl. I: 2 f. 6. Nar. bo- 

 realis Kt)Tz B. p. 9fi. Grun. Verh. 1860 p. 518. Lägst. Sp. D. Pl. I f. 4. A. S. Atl. Pl. XLV 

 f. 15—21. V. H. Syn. p. 76 Pl. VI f. 3, 4. Wolle Pl. IX f. 23. Pinnul. hebridensis Greg. M. J. 

 1854 p. 28 Pl. IV f. 13. Finn. ehilensis Rabh. Alg. Sachs. 885 (1859). 



On mosses, moist earth, in fresh water: Spitsbergen! Beeren Eiland (Lägst.), Greenland! 

 Iceland! Sweden! Finland! Germany! England! Belgium (V. H.), Switzerland! Japan! S:t Pauls 

 Island (Grun.), Sandwich Islands! Australia (Blue Mountains)! New Zealand! South Africa! 

 Argentina! Ecuador! W. lud. S:t Vincent! 



