SIBOGLINUM EKMANI 



189 



Fig. 99. Siboglinwn ekmani: 

 Spermatophore. 



a clear yellowish coloration, and at one pole it 

 is continued into a very long filament, whose 

 base is noticeably thickened. The sperm are 

 arranged parallel to the length of the spermato- 

 phore, filling its whole space (Fig. 99). The 

 length of a spermatophore is 0-15 mm. 



The tube consists of close-set, brilliant, 

 golden-brown or brown rings, regularly alter- 

 nating with transparent colourless intervals. 

 The rings are somewhat longer than the inter- 

 vals, sometimes much longer, and then their 

 brown colour becomes darker. They may be 

 irregular in form or incomplete, or their edges 

 may be uneven. Not infrequently two adjacent 

 rings may anastomose, and in the hinder part of 

 the tube they may run into one another (Fig. 

 9SD). The material of the rings is brittle. The 

 anterior limp part of the tube is transparent 

 and segmented, with the boundaries between 

 the segments rather prominent. In the ringed 



part of the tube each segment covers seven rings (Fig. 98 C), but exceptionally, 

 in the posterior part of the tube, segments may sometimes be found contain- 

 ing six or even five rings. The largest known fragment of tube measures 213 

 mm long, and the diameter varies from 0-12 to 0T6 mm. 



S. ekmani is allied to S. fedotovi, S. plumosum and S. pinnulatum by 

 several characters, namely, the arrangement of the pinnules in a double row, 

 the presence of a pretentacular groove and the tendency for the rings of the 

 tube to coalesce. With the last of these species, moreover, S. ekmani is 

 connected by the absence of any trace of a glandular belt in the mesosoma, 

 and by the presence of three girdles in the metasoma. Three girdles of 

 toothed platelets (two anterior and the third some way back) are, however, 

 likewise found in S. buccelliferum, S. hyperboreum and S. tenue (the last two 

 species lack pinnules). S. ekmani is distinguished from all known species by 

 the peculiar form of the pretentacular groove, by the form of the groove 

 between the protosoma and the mesosoma, and particularly by the dorsal 

 shields of the postannular region of the trunk. 



Material: I have had at my disposal four complete and a few incomplete 

 individuals, and also some fragments of tubes, from Kirkegaard in collections 

 from the Skagerrak. Jagersten had two incomplete specimens from the 



