132 



HYDROIDA II 



one the impression that only the extreme and thus latest developed gonothecse on the branches 

 can lack one or the other of the distal spines. This is different from what we find in Sertularia cu- 

 pressina, where the variants are distributed throughout the whole of the branch, without any distinctly 

 demonstrable regularity. Nutting (1904 p. 71) who mentions the fact that the gonothecse in Sertu- 

 laria Fabricii do vary, has not gone into the question of detail. 



The recent assignment of a previously undetermined specimen from the Kara Sea to Sertularia 

 Fabricii suggests that we have here a circumpolar species, capable of penetrating somewhat down into 

 the boreal areas. Further investigations will probably show the species to be more common in arctic 

 waters than would appear from the data on record. Sertularia Fabricii doubtless belongs, strictly speak- 

 ing, to the littoral region, but can, as shown by the finds at "Ingolf" St. 2, 3, and 4, also move some 

 way down into the abyssal. The species has previously been recorded from Alaska and Puget Sound. 

 Within the area investigated (fig. L,XX) it is noted from West Greenland, Jan Mayen, and the submarine 

 ridges between Iceland and the Faroe Islands, where the fauna is of a mixed character. 



Sertularia (?) tubuliformis (Marktanner-Turneretscher) Levinsen. 



1890 Dynamena tubuliformis, Marktanner-Turneretscher, Die Hydroiden des k. k. naturhistorischen Hof- 



museums, p. 238. 



1904 Thujaria tubuliformis, Nutting, Sertularidse, p. 70, pi. n, figs, i 8. 



1913 Sertularia tubuliformis, Levinsen, Systematic Studies on the Sertulariidae, p. 298. 



Upright pinnate colonies with alternating branches. The main stem has, on each internodium, 



on one side a branch and two hydrothecae, on the other a hydrotheca. The branch has in most cases 



minor branchlets oppositely 

 placed, and is divided by di- 

 stinct segmentation into inter- 

 nodia, bearing two to four, 

 generally three pairs of hy- 

 drothecae, of which the basal 

 ones are the largest, the di- 

 stal being the smallest The 

 internodium as a whole tap- 

 ers distally. The hydrothecae 



are set in more or less mark- 



LXXI. 



Part 



rtularia tubuliformis from "Ingolf ' St. 10. edly subaltemating, often al- 

 :olony showing an internodium with its 

 hydrotheca and the basis of two branches. 

 * Gonotheca. (X 40). 



most opposite pairs, and are 

 deeply imbedded. The free 



part of the adcauline wall is between one-third and one-fourth the length 

 of the hydrotheca, from half to once the opening diameter. The hydro- 

 thecae are of almost equal breadth throughout their length. The opening margin has two large lateral 

 teeth, and a more or less strongly developed median tooth in the adcauline sinus. The closing appa- 

 ratus consists of two membranes, of which the abcauline has a free distal part. 



