23 



Hornene gaar ud fra cellernes hjoriicr o^i, krydses ved 

 Tidgangspunktet ; do er temmelig lykke, bøiede, alle til 

 samme side af sagittalplaiiot, rettede ud fra kjedens bøi- 

 ningsaxe. Terminalliorn hverken i form eller retning foi-- 

 skjellige fra de øvrige.'*') 



Hvilesporer glatte, beliggende næsten midt i moder- 

 cellerne; skallerne lige hoit hvælvede, afrundet koniske. 

 Primærskallen med en ring af punkter langs den øvre rand, 

 sammenvokset med modercellens baand. som ved sporedan- 

 nelsen fortykkes og danner en kapi)e paa sporens overside. 



Vegetationstid. Hele aaret, især sommer og host. 

 Hvilesporer i august — november. 



Forekomst. Vestkysten og Christianiafjorden november 

 1893 (Hjort), Marstenen juni 95 {Hjort), vestkysten {Nord- 

 gaard) og ved Drøbak! februar 96, Bergensfjord juni — 

 august 96 (Nordf/aard), Drobak august (frk. Bonnevie) og 

 september! 96. 



Udbredelse. Atlanterhavet — Østersøen. 



19. Chætoceros debile, Cl. (1894) p. 18, Pl. I, fig. 2. 



Tab. nostr. II, fig. I4_i:,. 



Østrup 18!)o, p. 45G, T. VII, fi.?. 89. 



Syn. Ch. vermicidiis, Sohiitt (189')) p. 39, tig. 7 a — c. 



Kjederne spiralformig boiede, 12 — 39 u brede. 



Cellerne i frontstilling rektangulære med afruudede 

 hjørner, skallerne plane eller svagt konvekse, Ibramina af- 

 rundet rektangulære, noget indsnørede paa midten. 



Kromatofor 1, frontstillet. 



Hornene tynde, boiede, gaaende ud lidt indenfor skal- 

 lernes hjørner i skråa retning, krydsende hverandre ovenfor 

 udgangspunktet i hoide med kjedens rand, derefter af- 

 bøiede to transversalt til samme side af sagittalplanet, de 

 to andre sagittalt med en svag bøining i samme transver- 

 salretning, alle boiede ud fra kjedens bøiningsaxe. Ter- 

 minalhorn ikke forskjellige fra de øvrige. 



Hvilesporer midt i modercellerne, begge skaller ens 

 hvælvede, glatte, uregelmæssig topuklede. Primærskallen 

 bærer to enkle, butte horn, som gaar ud noget indenfor 

 randen diagonalt omtrent i retning af modercellens lijorner. 



Vegetationdid. Hele aaret. Hvilesporer i marts- 



juni. 



Forehmyist. Nordhavsexp. st. 296, Christianiafjorden 

 — Vestkysten november 93 (Hjort), Marstenen juni 95 

 (Hjort), Vestkysten februar 96 (Kordgaard), Urobak fe- 



*) Cleve beskriver og af bilder (1. c. l-<89, 1891) terminaihoni af eu 

 anden form og retning; dette beror dog sandsyuligvis paa en 

 sammenblanding af denne art med Ch. diadema eller Ch. constric- 

 tum, hvilke begge forekommer i hans materiale fra Gullmarsfjord. 

 Men begge disse arter har trausversalhornene rettede til modsat 

 side af sagittalplanet. 



Setæ issue from the angles of the cclls and cross at 

 their insertion; they are rather thick, all curvcd towards 

 the sTvme side of the sagittal plane, directed out from the 

 axis of the filamenfs curve. Terminal setæ not different 

 from the others either in shape or direction.*) 



Spores smooth. situated alinost in the middle of 

 the ])arent cells; valves equally convex, eonically rounded. 

 Primary valve with a ring of puncta along its su]jerior 

 margin, coalescid with the hoop of the parent cell, which 

 is thickened by the spore-formation, and forms a mantle 

 upon the upper surface of the spore. 



Per/od of Vegefatioii. Tiie whole year, especially 

 summer ;iiid autumn. Si)ores from Aug. to Nov. 



(Jccurrence. W.coast of Norway and Christiania Fjord. 

 Nov. 1893 (Hjort): Marstenen, June ISdb (Hjort); W.coast 

 of Norway (Nordqaard) and Drobak, Feb. 1896; Bergen 

 Fjord, June to Aug. 1896 (Nordgaard) ; Drobak. Aug. 

 (Miss Bonnevie) and Sept 1896. 



Distrihidion. Atlantic, Baltic. 



19. Chætoceros debile. Cl. (1894) p. 13, Pl. T. fig. 2. 

 ri. II, figs. 14, 1.-.. 



østrup 189.-), p. 4.i7, Pl. VII, fig. 89. 

 Syn. Ch. vermicidus, Schutt (189.')) p. 39, fig. ~ a — c. 



Filaments spirally curved, 12 — 39 /( wide. 



Cells, in a front view. rectangular witli rounded an- 

 gles, valves flat or slightly convex, foramina rounded lect- 

 angular, somewhat constricted in the middle. 



Chromatophore, 1, in front. 



Setæ thin. curvcd, issuing in an obli(|ue direction from 

 a little within the angles of the valves. crossing øne an- 

 other above their insertion on a level with the margin of 

 the filament, thcn turning off, two transversely to the same 

 side of the sagittal plane, the other two sagittally with a 

 slight curve in the same transverse direction, all hending 

 away from the axis of the chain's curvature. Terminal 

 setæ not differing from tiie others. 



Spores in the middle of the parent cells, valves equally 

 convex, smooth, each with 2 irregular humps. Pi-imary 

 valve carrying 2 simple, short and thick setæ issuing some- 

 what within the margin diagonally almost in tiic direction 

 of the angles of the i)arent cell. 



Feriod of Vcgefafion. The whole year. Spores ironi 

 March to June. 



Occurrence. Norw. N. Atlant. Exped. St. 296; Chri- 

 stiania Fjord, W.coast of Norway, Nov. 1893 {Hjort); 

 Marstenen, June 1895 (Hjort); W.coast of Norway, Feb. 



*) Cteve (1. c. 18^;9, l^'.\\) describes and figures terminal setæ of 

 another shape and inclination; this, however, is probably accounted 

 for by a confusion of this species with Ch. diadema or Ch enn- 

 strictum, both of which occur in his material from (jiillmars 

 Fjord; but both these species have the transversal setæ directed 

 to tlie opposite side of the sagittal plane. 



