46 p. T. CLEVE, SYX(n^SIS OF THE NAVICULOIU DIATOMS. 



and obi. stria; 24 ..^^ ja,;^^ i^ U,oi mm. — Donk. T. M. S. p. 21 PL III f. 2. V. H. Syn. p. 114 

 PI. XVII f. lU. Per. IX f. 18, 19. 



Marine: Coasts of Scotland and England! Belgium (V. H.)! Balearic Islands! Sumatra 

 (Deby Coll.)! 



Var. madagascarensis Grun. (1891). — Dorsal margin concave. L. 0,oi7 ; B. 0,03 mm. Median 

 line close to the dorsal margin. Transv. and obi. strite -"/jg in 0,oi mm. — T. madag. Per. p. 28 

 PL IX f. 13. 



Marine: Madagascar (Per). 



Var.? undulata Norm. (1861). — Dorsal margin gibbous in the middle, ventral triundulate. 

 L. 0,15; B. 0,032 mm. Transv. and obi. striee -"/m in 0,oi mm. — T. undulata Prit. Inf. p. 920 

 PL VIII f. 46 (1861). Per. IX f. 12. 



Marine: North Sea (Norm.). 



T. insignis seems to graduate into T. Gregoriana. 



2. T. Gregoriana Donk. (1858). — V. linear to semilanceolate, -with, unilaterally rounded 

 ends, curved in the same direction. Dorsal margin straight, ventral slightly convex. L. 0,i3 to 

 0,25; B. 0,022 to 0,03 mm. Median line arcuate, at the ends coincident with the margins. Transv. 

 and obi. striae ^"f^^, ^'/ai in 0,oi mm. — Donk. T. M. S. VI p. 19 PL III f. 1. Per. IX f. 16. 



Marine: Coasts of Scotland and England! 



Var. halearica Cl. (1878). — Dorsal margin slightly concave. L. 0,i7 to 0,22; B. 0,o2 to 0,025 

 mm. Transv. and obi. striae i'/i8> 'V19 in 0,oi mm. — T. halearica Cl. M. D. 154. Per. IX f. 14, 15. 

 Marine: Mediterranean Sea! 



3. T. Challengerensis Castr. (1886). — V. linear, narrow, inflated in the middle and at 

 the ends. L. 0,3; B. 0,oo4 mm. — Castr. D. Exp. Chall. p. 39 PL XXVI f. 14, 15. Per. IX f. 17. 



Marine: Tahiti (Castr.). 



Caloneis Cl. N. G. 



Valve usually convex, of various shape, linear, lanceolate, panduriform, rarely sigmoid and 

 asymmetrical. Striae usually parallel, and divergent in the ends (rarely convergent), not distinctly 

 (rarely finely) punctate, crossed by one or several longitudinal lines, which in some species increase 

 to broad, lateral areas. Connecting zone not complex. 



This genus comprises the groups abireviees, formosees, limosees and lineariees of Navicula 

 in the synopsis of Van Heurck, as well as the quadriseriatce of Grunow. All these groups are 

 intimately connected, however dissimilar the outline of the different species may be. Smaller 

 forms of Caloneis with indistinct longitudinal lines closely resemble small Pinnulariae, and certain 

 of the panduriform species seem to be very closely connected with some marine, panduriform 

 Pinnulariae. 



Pfitzer, who has examined the cell-contents of C. Silicula places this specis in his genus 

 Neidium, but it has no near afiinity with that genus. According to Pfitzer (Bau und Entw. p. 39) 

 there are as in Neidium tvfo chromatophores, lying closely along the inside of the connecting zone, 

 which do not migrate to the valves, but are divided in situ by fissures parallel to the longitudinal 

 axis of the cell. It thus appears that there are interior characteristics also, which distinguish 

 Caloneis from Navicula. — The cell-contents (of G, blanda, C. Liber and G. formosa) have also two 

 chromatophore-plates along the connecting zone. Their margins are entire. 



The form of the valve is as a rule linear, or lanceolate, and straight. A sigmoid species, 

 G. stanrophora, has hitherto been regarded as a Fleurosigma. This species has the ordinary form 

 of a Pleurosigma, but the following important characteristics induce me to place it in Caloneis: 



