KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 173 



This small and characteristic form is figured by Schumann with median line and central 

 nodule, of which I have never seen a trace. 



10. C. australis Petit (1877). — Outline elliptical. L. 0,02 64; B. 0,0242 mm. Upper V. 

 uuknown. Lower V. with sigmoid median line and the terminal nodules in contrary directions, at 

 some distance from the margin. Margin with rudimentary loculi. Striaä fine. — D. de Campbell 

 p. 11 Pl. IV f. 2. 



Marine: New Zealand (Petit). 



This species has the appearance of being very distinct, but it is, unfortunately, incompletely 

 described and figured. 



11. C. Van Heurckii Cl. N. Sp. — Elliptical. L. 0,035 to 0,04; B. O,oi.'i to 0,024 mm. 

 Upper V. with a straight axial silicions rib, sending ofF on both sides strong costfe, 4 to 5 in 0, 01 

 mm., connected by longitudinal silicious ribs, 2 to 4 on each side, thus forming a reticulum of 

 large, (|nadrate alveoli. Lower V. with straight median line, not reaching to the margin, and a 

 narrow, but distinct marginal area. Äxial area indistinct. Central area small, rounded. Striae 

 18 in 0,01 mm. slightly radiate, punctate. — Pl. II f. 32, So, 34. 



Marine : Madagascar ! 



The very peculiar upper valve of this species makes it doubtful whether it really belongs 

 to this group, but on the other hand the lower valve resembles that of G. Scutéllum. This 

 species may be the same as Cocc. surirelloides GtEUN. (Novara p. 98 Pl. I A f. 27, 28; 1867) but 

 the descriptions and hgure are insufficient for Identification. 



Eucocconeis Cl. N. G. 



Valves elliptical, rarely rostrate, without a marginal rim, ecostate, usually not very dis- 

 similar. Striation of both valves unusuaily delicate. U^sper valve with a narrow axial area. 

 Lower valve with straight or sigmoid median line. 



This group comprises most species of the old genus Cocconeis. Its affinities are difficult to 

 decide. In outline of the valves it resembles Cocconeis Cl., from which it is distinguished by the 

 absence of the loculiferous rim '). In the usually fine striation of both, not very dissimilar, 

 valves, it approaches 3ficroneis. C. flexella and C. minuta are isolated forms recalling Navicula 

 depressa and N. Rotaeana. 



Artificial hey. 



I ( Upper valve witli lateral areas or farrows 9- 



\ — — without ■ 2. 



J Upper valve with an uuilateral horseshoe-shaped marking 3. 



I — — withoat 4. 



( Striation fine, median line straight A. Calcar Cl. 



\ — coarse, — — sigmoid C. notata Pet. 



) Median line straight •• 5. 



\ — — sigmoid '• 



/ Median line reaching to the margin 6. 



\ — — not C. molesta KtJTz. 



( Striaj of the upper valve fine (20 in 0,01 mm.) C. finmarchica Grun. 



\ — — — — roarse (8 — — ) C. septentrionalis Grdn. 



/ Marine habitat C. dirupta Geeg. 



\ Fresh water habitat 8. 



J Axial area rlilated in the middle ■ .... C. minuta Cl. 



\ — — not — — — C. flexella Bréb. 



loculi. 



') In the collection of E. Grove I have seen some speeimens of C. dirupta from Australia which had rudimentary 



