76 P. T. CLBVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Finn. subcapitata of GtEEGORY has uninterrupted strise, biit forms with a transverse fascia 

 are much more frequent. This species seems to graduate into Finn. interrivpta, from which it 

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



9. P. interrupta W. Sm. (1853). — V. linear, with parallel or slightly concave margins 

 and capitate ends. L. 0,0 5 to O,o7 6; B. 0,oi.3 mm. Axial area narrow, dilated in the middle to 

 a rhomboid space or transverse fascia. Strise 10 to 15 in 0,o i mm., strongly radiate in the middle, 

 convergent at the ends. 



Forma biceps: central area rhomboid. — P. biceps Grbg. M. J. IV p. 8 Pl. I f. 28 (1856). 

 F. interrupta ii W. Sm. B. D. II p. 96. Nav. mesolepta /? producta Grun. Verh. 1860 p. 520 Pl. IV 

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

 biceps A. S. Atl. XLV f. 69, 70. Nav. Ternies A. S. Atl. XLV f. 67. Nav. mesolepta var. boryana 

 Pant. III Pl. XXI f. 312. 



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

 Australia, Blue Mountains! Brazil! 



Forma stauroneiformis : central- area a transverse fascia. Finn. interrupta W. Sm. B. I). XIX 

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

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



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

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



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

 L; 0,035 to 0,042; B. 0,oo8 to 0,012 mm. Strise 13 to 14 in 0,oi mm. — Nav. globiceps var. crassior 

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



Brackish water: Jamal (Kära Sea)! Åland (Baltic)! 



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

 margins. There is the same conuection between them as between F. clivergens and F. Legumen. 



10. P. mesolepta Ehb. (1843). — V. trinndulated, with capitate ends. L. 0.o3 to 0,o6; 

 B. 0,0 11 mm. Axial area narrow, dilated in the middle. Strite 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. Kutz 

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

 W. Sm. b. D. XIX f. 182. Nav. mes. var. 0, genuina Grun. Verh. 1860 p. 520. 



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



Var. stauroneiformis Grun. (1860). — Central area a transverse fascia, widened towards the 

 margins. — Grun. Verh. 1860 p. 520 Pl. IV f. 22 b. A. S. Atl. XLV f. 52, 53. 



Fresh water: Sweden (Rosslängen, Upsala)! Finland! Greenland! Canada! Bridgewater, Maine! 



Var. angusta Cl. — V. narrow linear, triundulate. L. 0,o65 to O.os; B. 0, 009 to 0, 01 mm. 

 Axial area wider. Striee 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! Ringkiöbing, Denmark (Atl.), Harz (Atl.), Maine, Bridge- 

 town! iJemerara River! Rio Purus, Brazil! 



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

 others. L. 0,ofi to 0,o8; B. 0,012 mm. Area narrow, gradually expanded towards the middle to a 

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

 polyonca Bréb. in Ktltz Sp. Alg. p. 85. V. H. Syn. p. 80 Suppl. A. f. 14. Nav. mesotyla A. S. 

 Atl. XLV f. 54, 55. 



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



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

 latter it differs by its narrower area. The var. polyonca is in all respeets to F. mesolepta what 

 the var. Formica is to F. nodosa. 



