KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 9.5 



Nav. retusa Bréb. seems to be a form, akin to Nav. cancellata, and therefore entirely dif- 

 ferent from this species, which I have, with much hesitation, placed in Pinnularia. 



Var. {Amphora) Digitus A. S. (1875). — V. asymmetrical. L. 0,05 to 0,i; B. 0,oo7 to0,oi2 

 mm. Axial area asymmetrical, a little broader on the dorsal side. Strise 8 in 0,oi mm., not dis- 

 tinctly punctate. Frustule rectangular. Connecting zone with several faint longitudinal divisions, 

 which are finely transversely lineate; lineolfe 24 in 0,oi mm. — Amphora Digitus A. S. Atl. XXVI 

 f 30. Cl. and Grove Diatomiste I p. 67 Pl. X f. 11 to 13. 



Marine: North Sea! Griiernsey (Grove Coll.)! Balearic Islands! Macassar Straits! China! 



71. P. bistriata Leud. Fortm. (1879). — V. linear, with rounded ends. L. O.05.5 to 0,o65; 

 B. 0,009 mm. Central nodule transversely dilated. Axial area narrow; central area a broad, trans- 

 verse fascia. Strite 10 in 0, 01 mm. radiate in the middle, transverse or convergent at the ends. 

 — Sfauronris bistriata Leud. Fortm. D. Ceylon Pl. IX f. 89. 



Marine: Mediterranean Sea (Barcelona)! Ceylon (Leud. Fortm.). Labuan! 

 I have seen only two valves of this characteristic form and I have placed it in Pinnularia 

 with great hesitation. 



72. P. quadratarea A. S. (1874). — V. narrow, linear, with parallel margins and broad 

 rounded extremities. L. 0, 01 to 0, 09; B. O,oii mm. Median line with small terminal iissures. 

 Axial area indistinct or very narrow; central area a broad fascia. Striee parallel, 8 to 10 in 0,oi 

 mm. — Nav. Pinnularia Cl. (1868) Sv. N. D. p. 224 Pl. IV f. 1, 2. Nav. quadrat. A. S. N. S. D. 

 p. 90 Pl. II f. 26. 



Marine: Arctic Seas (Arctic America, Spitsbergen, Finmark, Novaja Zembla, Cape Wanka- 

 rema)! North Sea (Bohuslän, Sweden)! Mediterr. (Balearic Islands)! Australia Sydney! 



This species was first described by me as Nav. Pinnularia, and låter by A. Schmidt as Nav. 

 cjuadratarea, but as my specific name would be inadmissible I have given preference to the name 

 of A. Schmidt. It is a very variable species, of which a great number of forms has been described 

 as distinct species, but as they are closely connected I have united them. The chief distinction 

 consists in the outline and the number of strise. Closely connected with some of the varieties (Var. 

 fluminensis etc.) are P. floriduna Cl. and P. cruciata. On the other hand the var. Théelii approaches 

 to P. cruciformis Donk. The varieties may be arranged in the following series. 



A. Forms with linear, not consfricted valves. 



Var. haltica Grun. (1880). — B. 0,oo8. Striee 9 in 0,oi mm. — Nav. Pinn. var. balt. 

 Grun. a. D. p. 27. 



Brackish water: Baltic (Grun.). 



Var. Seychellensis Grön. (1880). — V. sbort, linear, with rounded ends. B. O,oii mm. 

 Strise 12 in 0,oi mm. — Nav. Pinn. var. Seych. Grun. A. D. p. 28. 



Marine: Seychelles (Grun.). 



Var. Söderlundii Cl. (1880). — V. linear, with rounded ends. L. 0,o36 to 0,045; B. 0,oo6 

 to 0,007 mm. Strise 13 to 16 in 0,oi mm. — Nav. Pinn. var. Söderl. Cl. A. D. p. 28. 



Marine: Davis Strait! Balearic Islands! Tahiti! 



Var. Tahitensis Grun. (1880). — V. linear, with subcuneate ends. B. 0,oo9 mm. Strise 13 

 in 0,01 mm. — Nav. Pinn. var. Tah. Grun. A. D. p. 28. 



Marine: Tahiti (Grun.). 



Var. interrupta Cl. (1883). — V. linear, with subcuneate ends. L. O, os; B. 0,02 mm. 

 Strise 9 in 0,oi mm., crossed by irregular, longitudinal, blank bands. — Nav. Pinn. var. interr. 

 Cl. Vega p. 463 Pl. XXXVI f. 21. 



Marine: Cape Wankarema! 



