HYDROIDA II 



127 



considerably into the arctic areas, and also southward into warmer seas; it is mentioned from the 

 Mediterranean to Nova Zembla, but the most numerous finds have been made in the boreal region. 

 The species is known from both sides of the Atlantic, and also from the Pacific, which renders its 

 occurrence within the area investigated the more remarkable (fig. LXVI). It is very common in the 

 British waters, and along the west coast of Norway, and is now found to be common also at the Fa- 

 roe Islands and on the east, south and west coasts of Iceland. It has not however, yet been recorded 

 from Greenland, where there would seem every reason to expect it, since it is known from the arctic 

 waters off the east coast of America. The reason of this peculiarity must for the present be left an 

 open question. Sertularia cupressiua has its chief occurrence in the upper half of the littoral region, 

 and is only extremely rarely met with in the abyssal. 



200 m. boom. 1000 m. 2 000 m. 



Fig. LXVI. The distribution of Sertularia cupressiua in the Northern Atlantic. 

 In the hatched regions a common occurrence is stated. . 



Sertularia tenera G. O. Sars. 

 1874 Sertularia tenera, G. O. Sars, Bidrag til Kundskabeu om Norges Hydroider, p. 108, pi. 4, figs. 1 — 4. 

 1874 Sertularia arctica, Allman, On the diagnosis of new genera and species of Hydroids, p. 179. 

 1884 Sertularia aldimaris, Thompson, The Hydroid Zoophytes of the "Willem Barents", p. 3, pi. 1, figs. 



nee 1877 Sertularia aldimaris, Mereschkowsky, On a new genus of Hydroids p. 228. 



1887 Sertularia argent ea -- S. DijmpkncB, Bergh, Goplepolyper (Hydroider) fra Kara-Havet, p. 335, pi. 



28, fig. 3. 



1899 Dynamena unilateralism Bonnevie, Den norske Nordhavs-Expedition, p. 78, pi. 7, fig. 5. 



1901 Sertularia TJiompsoni, Schydlowsky, Les Hydraires de la Mer Blanche. 



