HYDROIDA II 



'43 



in the material from the cruise of the "Dijmphna" in the Kara Sea, but has there erronously been 

 referred either to Thujaria lonchitis or Thujaria articulata. From its arctic home, the species also 

 spreads out into the boreal region (fig. LXXVII) where it has been recorded from the Faroe Islands 

 and Iceland, and in Davis Strait. It will presumably also be found to occur off the coast of Norway, 

 but in these waters, it has not hitherto been distinguished from Thujaria lonchitis, so that we have 

 no reliable data up to the present. 



200 m. boom. . ._ _ ...looo m. 



Fig. LXXVII. Finds of Thujaria laxa in the Northern Atlantic. 



Thujaria alternitheca Levinsen. 

 1893 Thujaria alternitheca, Levinsen, Meduser, Ctenophorer og Hydroider, p. 52 pi. 7, figs. 1520. 



Robust, upright colonies with spiral, monosiphonic stem. The stem is divided by distinct seg- 

 mentation into internodia of varying length, and has two single spiral tiers of hydrothecae; there are 

 from 3 to 6 hydrothecse between two successive branches in the same spiral, the lowest in the branch 

 corner. Normally, the sixth branch will be found straight above the first in the same tier. The broad plane 

 of the branches is perpendicular to the axis of the stem (lies horizontally) and the branches form, at 

 their point of origin, almost a right angle with the stem, afterwards curving somewhat downwards; 

 they are secondarily branched dichotomously, and divided into internodia with five or more pairs of 

 hydrotheca;. The hydrothecEe of the branches form two very close longitudinal rows; the hydrothecse 

 are closely set, each thrusting its opening part out upwards and sideways beyond the next, displaced 

 alternately to either side of the median line through the base of the hydrothecse, presenting a distinct 

 approach to quadriserial arrangement. The hydrothecae are entirely imbedded in the stem and bran- 

 ches, without any free distal part of the adcauline wall. The opening is circular, the margin without 

 teeth or sinus, with a large round opercular plate abcaulinally attached. 



