3. Pleurosigma (Donkinia?) longissimum Cl. N. Sp. 



Very long and narroAv, liiiear; ends obtuse. Median lirie straight in the middle 

 but curved in the last third part from the central nodiile. Striaj in two sets crossing 

 each other in right angles, transverse I8V2) longitudinal 21 in 0,01 mm. Colcur 

 påle straw. 



Length of the frustule 0,17 mm. Breadth 0,0083 mm, 

 Pl. I, fig. 8. a. ''"/,; b. structure """/i- 



Balearic Islets rare (leg. Dr. Söderlund). 



Rlioicosigma Grun. 



1. Rlioicosigma mediterraneum Cl. (in Grun. Mior. Journ. 1877, p. 182). 



Narrow lanceolate, with acute ends. Median line strongly bent in the first third 

 part from the central nodule, afterwords straight. Strias longitudinal and transverse. 

 The longitudinal stria3 are very fine, about 27 in 0,01 mm., the transverse 18^/^ in 

 0,01 mm. 



Length 0,18—0,21 mm. Breadth 0,0225 mm. 



Pl. I, fig. 9, "V,, a. and b. valves, c. structure -"»7,. 



Balearic Islets rare (leg. Dr. Söderlund). 



Navicula Bory. 



1. Navicula {Fluminensis var.?) Floridana Cl. N. Sp. 



Elongated, slightly constricted in the middle, ends rounded. Striaj not distinctly 

 punctate, parallel, 15 in 0,01 mm., closer near the ends, 2U in 0,01 mm., absent from 

 the middle part of the valve, not reaching the median line, which is surrounded by a 

 narrow, linear area. 



Length 0,045—0,075 mm. Breadth 0,01—0,012 mm. at the constriction 0,08 — 

 0,009 mm. 



Pl. I, tig. 10, ^»°%. 



Florida coast, near Pensacola Harbour (in a gathering sent by Mr. Febiger). 



2. Navicula cruciata Cl. N. Sp. 



Oblong, slightly contracted at the centre. Striaj 12 in 0,01 mm., parallel, costate, 

 smooth or indistinctly granulate, absent from the middle part of tlie valve, not 

 reaching the median line. 



Length 0,087 mm. Breadth 0,017 mm. at the middle 0,014 mm. 



Pl. I, Fig. 11, ^""V,. 



I have found this species in a sample, said to be from Greenland, but as it con- 

 tained many tropical forras, I am not sure that this is correct. 



