KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 95 



Nav. retusa Br^b. 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. Striae 8 in 0,oi mm., not dis- 

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

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

 f. 30. Cl. and Grove Diatomiste I p. 67 PI. X f. U to 13. 



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



71. P. bistriata Leud. Fortm. (1879). —V. linear, with rounded ends. L. 0,o5.5 to 0,o65; 

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

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

 — Stauroneis bistriata Leud. Fortm. D. Ceylon PI. 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,oi to 0,o9; B. 0,on mm. Median line with small terminal fissures. 

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

 mm. — Nav. Pinnularia Cl. (1868) Sv. N. D. p. 224 PI. 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 (Bohuslan, Sweden)! Mediterr. (Balearic Islands)! Australia Sydney! 



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

 quadratarea, 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. floridana Cl. and P. cruciata. On the other hand the var. Theelii approaches 

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



A. Forms with linear, not constricted valves. 



Var. haltica Grun. (1880). — B. 0,oos. Striee 9 in 0,or mm. — Nav. Pinn. var. bait. 

 Grun. a. D. p. 27. 



Brackish water: Baltic (Grun.). 



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

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



Marine: Seychelles (Grun.). 



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

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



Marine: Davis Strait! Balearic Islands! Tahiti! 



Var. Tahitensis Grun. (1880). — V. linear, with subcuneate ends. B. 0,oo9 mm. Striae 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. 0,08; B. 0,02 mm. 

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

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



Marine: Cape Wankarema! 



