11 



3. Chætoceros danicum, Cl. (1885) p. 55. 



Descr, Cleve (lfs<)4) p. 12. 



Fig. Ch. Wighami, Van Heurck. Synopsis. T. 82, fig-. 1. 

 Forel-u)Hst. Kristianiatjordfu, sji^lJen. 

 Udhreclelse. Østersøen — Kattegat. 



4. Chætoceros Brightwellii, LI. T. I, tig. l a-c. 



Syn. Chætoceros boreale ,i BrUjhttveUU , Cl. (1873, 13) T. II. 

 Hir. ~ /'. r, r, 



— convolufiiiii, Castr. (1880) p. 77. 



— boreale. Cl. p. p. (ls<t4) p. 12. 



Kjedeine rette, bredde 12—24 u., deres ender for- 

 skjellige, hornene boiede fra den øvre mod den nedre. 

 Cellerne i frontstilling rektangulære, hjornerne paa over- 

 siden afrundede, paa undei-siden skarpe. Skallerne ulige. 

 den ene hvælvet, den anden næsten plan. Hornenes ud- 

 gangspunkter udcnfor sagittalplanet. linjen niellem dem gaar 

 gjennem kjedens længdeaxe og danner en spids vinkel 

 afvekslende paa begge sider af sagittalplanet. XJdgangs- 

 punkterne ligger paa den plane skal nær randen, paa den 

 konvexe nærmere midten. Hornene temmelig tykke, nær 

 udgangspnnktet bøiede; tornene mindre end hos CJi. horeale. 

 Foramina fladt trapezformede eller ganske lukkede af de 

 skjævt udgaaende horn. 



Udbredelse. Atlant erha vet. 



Subiieiiiis II. 



Hyalochæte, Chan mscr. 



Hornene tynde, farvelose. Cellekjerne vægstillet, kro- 

 matoforer pladeformede, vægstillede. Hvilesporer kjendes 

 hos de fleste arter. 



A. Kromatoforer flere end to i liver celle. 



a. Grove kjeder med difterentierede terminalhorn. 



* Kromatoforer 4 — 10 større plader, hornene sammenvoksede 

 et kort stykke efter længden. .'). Ch. decijjiens, Cl. 



** Kromatoforer talrige smaa plader, hornene kun ved ud- 

 gangspnnktet sammenvoksede. li. Ch. teres, Cl. 

 6. Spædere kjeder uden difterentierede terminalhorn, men paa 

 nogle steder med intermediære horn fortykkede, longitudinalt 

 afbøiede i samme retning. 



7. Ch. contortnm, Schiitt. 



B. Kromatoforerne trykkede op mod skallernes bund, 2 (hos Ch. 

 laeiniosum undertiden 1) i hver celle. 



I. Kjedenie rette, hornene direkte sammenvoksede. 



a. Foramina todelte, skallerne berører hinanden i midten. 



8. Ch. simile, Cl. 

 6. Foramina udelte, skallerne konkave. 



* Skallerne med en halvkugleformig udvækst i midten, 

 sporerne helt ensidig i modercellerne, sammenknyttede 

 parvis t'- Ch. dklymum, Ehr. 



** Skallerne konkave, paa midten svagt eller ikke hvæl- 

 vede, spoilerne enkeltvis. 



3. Chætoceros danicum. Cl. (1885) \). 55. 



Descr. Cleve (18',U) p. 12. 



Fig. C/i. Wighami, Van Heurck Synopsis. Tl. 82, fig. 1. 



OccurrvHce. Christiania Fjord. rare. 

 Distribiifioii. Baltic. Kattegat. 



4. Chætoceros Brightwellii, Cl. Pl. 1, tig. 1 a—c. 



.Syn. Cliætocerot: Imreiilr .1 Britjhtivellii Cl. (1873, 131 Tl. II, 

 fig. 7 b, c, e. 



— convolutum Castr. (188fi) p. 77. 



— boreale Cl. p. p. (18<I4) p. 12. 



Filaments straight, width 12 — 24 ii. extremities dif- 

 ferent, the setæ bent from the upper towards the lower. 

 Cells, in a front view. rectangular, the angles on the upper 

 side rounded. on the under side sharp. Valves unequal, 

 the one coiivex, the other almost flat. Insertions of the 

 setæ outside the sagittal i)lane. tiie line between them 

 passing through the long axis of tiie filameut, and forming 

 an acute angle alternately on each side of the sagittal 

 plane. The insertions upon the flat valve are near the 

 edge, upon the convex valve, nearer the middle. Setæ rather 

 thick, curved near the point of issue; spines fewer than in 

 Clu horeale. Foramina flatly trapeziform in shape, or coni- 

 pletely closed by the oljliquely projecting setæ. 



Distrihdhiii. Atlantic Ocean. 



Sub-geniis II. 



Hyalochæte, Gran mscr. 



Setæ thin, colourless. Xucleus situated in tiie wall; 

 chromatophores lameUiform, situated in the wall. Spor^ 

 found in most of tiie species. 



A. Chromatophores more than 2 in each cell. 



a. Coarse filaments with differentiated terminal setæ. 



* ChronuUophores 4 — li) large lamellæ; setæ coalesced for 



a short portion of their leugth. ,'). Ch. decipiens, Cl. 



** Chromatophores numerous small lamellæ; setæ coalesced 



only at the insertion. 0. Ch. tei-es, Cl. 



6. More sleuder filaments without differentiated terminal setæ, 



but in some places with intermediai-y setæ thickened and 



longitudinally dcflected in the same direction. 



7. Cli. eontortnm, Schiitt. 



B. Chromatophores prcssed close up to the bottom of the valves, 

 2 in each cell (in Ch. laeiniosum sometimes 1). 



I. Filaments straight, setæ directly coalesced. 



a. Foramina lii-partite, valves touching one another in the 



middle. 8. .C/(. simile. Cl. 



h. Foramina single, valves concavc. 



* Valves with a hemispherical protuberance in the mid- 

 dle, spores situated quite at one side, connected in pairs. 



9. Ch. didymum, Ehr. 

 ** Valves concavc, not convex. or only slightly so. in the 

 middle; spores single. 



2» 



