46 P. T. ('LEVE, SYNOPSIS OK TUK XA VKTLi >| l) OlATOMS. 



and obl. striffi ^^/.,^, ■"/„, in U.oi mm. — DoNK. T. M. S. p. 21 Pl, 111 f. -2. V. H. Syn. p. 114 

 Pl. XVII f. 10. Per. IX f. 1«, 19. 



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

 (Deby Coll.)! 



Var. 'inadaijascarciisis Grun. (1891). — Dorsal margin concave. L. 0,oi 7 ; B. 0,ii3 mm. Median 

 line close to the dorsal margin. Transv. and obl. stritt '-"/ig in 0,oi mm. — T. muda<j. Per. p. 28 

 Pl. IX f. 13. 



Marine: Madagascar (Per). 



Var.? loidnhita Norm. (1861). — Dorsal niargin gibbuus in the middle. ventral triundulate. 

 L. 0,1.0; B. 0,032 mm. Transv. and obl. stria' -"',„ in 0, 01 mm. — T. unchdaiu Prit. Inf. p. 920 

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



Marine: Noi'th Sea (Norm.). 



T. insignis seems to graduate into T. Gregoriana. 



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

 ends, ciu'ved in the same direction. JJorsal margin straight, ventral slightly convex. L. 0, 13 to 

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

 and obl. strife ^o/jg, 21/,, 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. balearica Cl. (1878). — Dorsal margin slightly concave. L. 0,i7 to 0,22; B. 0, 02 to 0, 025 

 mm. Transv. and obl. stricE i'/,g, 'Vid in 0,oi mm. — T. halearica Cl. M. D. 154. Per. IX f. 14, 15. 

 Marine: Mediterranean Sea! 



3. T. Ohalleiigereiisis 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 nsually convex, of varions shape, linear, lanceolate, pandnriform, rarely sigmoid and 

 asymmetri cal. Strite nsually parallel, and divergent in the ends (rarely convergent), not distinotly 

 (rarely finely) punotate, crossed bj^ one or several longitudinal lines, which in some species increase 

 to broad, lateral areas. Connecting zone not complex. 



This genus comprises the gronps abhréviées, formosées, liniosées and Uneariées of Navicnla 

 in the synopsis of Van Heurck, as well as the qiiadriscriafa of GRUNO^v. All tliese groups are 

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

 forms of Caloneis with indistinct longitudinal lines closely resemble small Pinnularite. and certain 

 of the pandnriform species seem to be very closely connected with some marine. pandnriform 

 Pinnnlariaj. 



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

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

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

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

 axis of the cell. It thus appears that tlierc are interiör eharacteristics also, which distinguish 

 Caloneis from Navicnla. — The cell-contents (of O. blanda, C. Liber and C. foniiof<a) have also two 

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



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

 G. sfaAirn^phora, has hitherto been regarded as a Plcurosigma. This species has the ordinary form 

 of a Plenrosigma, Imt the following important eharacteristics indnce me to place it in Caloneis: 



