76 p. T. CLEVE, SYNOPSIS OF THE NAVICULOIU DIATOMS. - 



Finn. !<ubcaintata of (tREGory has uninterrupted striffi, but forms with a transverse fascua 

 are much more frequent. This species , seems to graduate into Pinn. interrupta, from which it 

 differs principally by its smaller size and less distinctly capitate ends. 



9. P. iiiterrupta W. Sm. (1853). — V. linear, with pp,rallel or slightly concave margins 

 and capitate ends. L. 0,05 to 0,076; B. 0,oi.3 mm. Axial area narrow, dilated in the middle to 

 a rhomboid space or transverse fascia. Stria' 10 to 15 in 0,oi mm., strongly radiate in the middle, 

 convergent at the ends. 



Forma biceps: central area rhomboid. — P. biceps Gtreg. M. J. IV p. 8 PI. I f. 28 (185(i). 

 P. interrupfa li W. Sm. B. D. II p. 96. Xar. mesohpfa (i producta Grun. Verb. 1860 p. 520 PI. IV 

 f. 22 a. Nav. bicapitata Lagst. Spitsb. D. p. 23 PI. I f. 5. V. H. Syn. p. 78 PI. VI f. 14. Nav. 

 biceps A. S. Atl. XLV f. 69, 70. Nav. Termcs A. S. Atl. XLV f. 67. Nav. mesolepta var. bori/cuta 

 Pant. Ill PL XXI f. 312. 



Fresh water: Spitsbergen! Norway! Sweden! Finland! Scotland ((Ireg.), Siberia! Japan! 

 Australia, Blue Mountains! Brazil! 



Forma sfaiironcifnrmis: central area a transverse fascia. Finn, interrapta W. Sm. B. 1). XIX 

 f. 184. Nav. int. A. S. Atl. XLV f. 72, 75, 76. Nav. Termes oar. stauroneif. V. H. Syn. PI. VI 

 f. 12, 13. A. S. Atl. XLV f. 71. 



Fresh water: Greenland! Norway (Romsdalen)! Sweden! Finland! England (W. Sm.), (ler- 

 many (Atl.), Bengal! Sandwich Islands! Surinam! Brazil! 



Var. crassior Grun. (1880). — V. gibbous in the middle and with broad, capitate ends 

 L. 0,03.5 to 0,042; B. 0,008 to 0,0 12 mm. Stripe 13 to 14 in 0,oi mm. — Nav. ylobiceps var. crassior 

 Grun. a. D. p. 27 PI. I f. 13. A. S. Atl. XLV f. 79 (without name). 



Brackish water: Jamal (Kara Sea)! Aland (Baltic)! 



Finnul. biceps is closely connected with P. mesolepta, which differs only in the triundulate 

 margins. There is the same connection between them as between P. divergens and P. Legumcn. 



10. P. mesolepta Ehb. (1843). — V. triundulated, with capitate ends. L. O.0.3 to O.oe; 

 B. 0,011 mm. Axial area narrow, dilated in the middle. Stride 10 to 14 in 0,oi mm. strongly 

 divergent in the middle and convergent at the ends. — Nav. mesolepta, Ehb. Am. IV: 2 f. 4. KtJTZ 

 Bac. p. 101 PI. XXVIII f. 73, XXX f. 34. V. H. Syn. p. 79 PI. VI f. 10-11. Finn, mesolepta 

 W. Sm. B. I). XIX f. 182. Nav. mes. var. a, genuina Grun. Verb. 1860 p. 520. 



• Fresh water: England! Scotland! Greenland! New Zealand! 



Var. stanroneiformis Grun. (18()0). — Central area a transverse fascia, widened towards the 

 margins. — Grun. Verb. 1860 p. 520 PL IV L 22 b. A. S. Atl. XLV L 52, 53. 



Fresh water: Sweden (Rosslangen, LTpsala)! Finland! Greenland! Canada! Bridgewater, Maine! 



Var. ainiHsta Cl. — V. narrow linear, triundulate. L. 0,06.5 to O.os; B. 0,oo'j to 0,oi mm. 

 Axial area wider. Stria; 10 to 13 in 0,oi mm. — Nav. gracillima A. S. Atl. XLV f. 62. Cl. 

 M. D. N:o 103. 



Fresh water: Upsala, Sweden! Ringkiobing, Denmark (Atl.), Harz (Atl.), Maine, Bridge- 

 town! Lemerara River! Rio Purus, Brazil! 



Var. polyonca Br^b. (1849). — V. triundulate; the median inflation being larger than the 

 others. L. 0,o6 to 0,08; B. 0,012 mm. Area narrow, gradually expanded tow^ards the middle to a 

 stauros. Striae 11 to 12 in O.oi mm., divergent in the middle, convergent at the ends. — Nav. 

 polyonca Br^b. in Kiitz Sp. Alg. p. 85. V. H. Syn. p. 80 Suppl. A. f. 14. Nav. mesotyhi A. S. 

 Ati. XLV f. 54, 55. 



Fresh water: Sweden (Loka, Atl., Uj)sala!) Belgium (V. H.). 



P. mesolepta is nearly connected with P. interrupta and analogous to P. nodosa,, from which 

 latter it differs by its narrower area. The var. polyonca is in all respects to P. mesolepta wbat 

 the var. Formica is to P. nodosa. 



