KONUL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 18. N:(i 5. 5 



Length 0,035-0,06 mm. Breadth 0,012-0,015 mm. 



Pl. I, lig. 4, a. (dry), b. (balsam); ""7,. 

 Brazil, fresh water, collected by Dr. Wahming. (Cl. et Moll. Diat. N:o 193.) 

 In the stroDgly marked central striaa this form reminds one oi Navicula Criicicula, 

 but it is quite different. There is also some resemblance to the Navicula Lundströmii 

 Cl. (in Cl. et Grun. Arctische Diat. Pl. III, fig. 39). Another allied form is the as 

 yet undescribed Cymhella Fruseana Gkun. from Tana Elf in Finmarken (Cl. et Moll. 

 Diat. N:o 261). This species has produced and capitate ends and 12 — 15 punctate 

 strise in the middle, 18 — 19 halfway between the middle and the ends, where they are 

 21 in 0,01 mm. Length 0,05 — 0,06 mm. Breadth 0,014 mm. 



2. Cymhella Stodderi Cl. N. Sp. 



Elongate, lanceolate, slightly as3'mmetrical. Ends slightly produced and attenuated. 

 Stria3 strongly radiant in the middle, almost pai^allel near the apices, scarcely punctate, 

 10 in 0,01 mm. a little more distant in the centre, covering % of tbe valve and 

 leaving on both sides of the median line a tolerably broad area. 



Length 0,075—0,09 mm. Breadth 0,015 mm. 

 Pl. I, iig. 5; '"""/i (Specimen from Brazil). 



Fossil: Bemis Lake in White Mountains (Mr. Stodder). Living: Brazil, Minas 

 Geraes on Sphagna leg. Dr. Hj. Mosén. 



This species, which occurs in Cl. et Möll. Diat. N:o 212 and N:o 274, is most 

 nearly related to the C. Americana A. Schm. Atl. Pl. IX, fig. 15 and 20, but the latter 

 form has a more narrow area and, as fig. 15 shows, punctate strite. 



Pleurosigma W. Sm. 



1. Pleurosigma tortuosum Cl. N. Sp. 



Median line strongly and equally sigmoid. Stria3 in three sets, oblique 21, trans- 

 verse 22 in 0,01 mm. 



Length 0,076 mm. Breadth 0,008 mm. 



Pl. I, fig. 6; -°7x. 

 Balearic Islets (Dr. Söderlund) rare. 



2. Pleurosigma lanceolatum var. cuspidatum Cl. 



Lanceolate with produced apices, symmetrical. Median line stx^aight, the ends 

 tnrned in opposite directions. Stri^ in three sets, one transverse (20 in 0,01 mm.) 

 and two oblique (22 in 0,01 mm.). 



Length 0,083 mm. Breadth 0,02 mm. 

 Pl. I, fig. 7; ""7,- b. structure; ^«°%. 



Marine: Port Jackson (Eugenia Exp.). 



The same variety from Newcastle has according to Grunow 20 transverse and 19 

 oblique striaä in 0,01 mm. Length 0,105 ram. Breadth 0,026 mm. 



