HYDROIDA II 



III 



of the stem, the one hydrotheca in the branch corner. Finally, the branches and the colonies are 

 curved, so as to present a distinctly convex foreside; the branches themselves also, are not infrequentlv 

 again ramified. The colonies are thus typical transition forms, and as such occur in all shades of 

 difference between the typical main form and the extreme, regularly pinnate variants, we cannot 

 separate the latter as a distinct species. 



Kramp (1914 p. 1053) has very appropriately characterised Diphasia fallax as "an atlantie 

 boreal species only sporadically found in arctic regions". Its occurrence in the north Atlantic (fig. 

 LIX) shows, however, that it is still not quite universal in the boreal waters; it appears, strangely 

 enough, to be very rare off the west coast of Greenland, where we should otherwise have expected to find 

 it of common occurrence in the mixed company of southern and northern forms found in Davis Strait. 

 Bathymetrically, its chief occurrence falls in the middle and lower part of the littoral region, and the 

 upper part of the abyssal; at times it ma}- penetrate far down into the latter, as is shown by the list 

 of finds from the "Ingolf". It is consequently the more remarkable that Diphasia fallax should seem 

 to disappear at a somewhat greater distance from the coasts. A glance at the chart shows that the 

 species has very rarely indeed been taken far from islands or continent, and this cannot be accidental, 

 since the investigations both of the "Ingolf" and later expeditions have been carried out to a very 

 great extent in the open sea within the areas in question. The explanation of this must be left to 

 future studies. 



Diphasia Wandeli Levinsen. 



1893 Diphasia Wandeli, Levinsen, Meduser, Ctenophorer og Hydroider, p. 55, pi. 8, figs. 1 — 5. 



Upright pinnate colonies with pronounced dark monosiphonic main stem. The stem is divided 

 by transverse nodes into short internodia, each bearing a pair of hydrotheca; placed oppositely, and a branch 

 under the base of the one, turning alternately to either side of the stem. The branches are likewise 

 divided up into short internodia, each having three hydrothecas in a wreath ; there are thus three rows 

 of hydrothecse on each branch. The hydrothecse are deeply embedded; the adcauline wall has a free 

 distal part about one-fifth to one-fourth the length of the hydrotheca, between half and once the 

 opening diameter. The opening is set almost perpendicular to the branch axis; the margin has a 

 slight adcauline sinus, in which the large opercular plate is attached. 



The gonothecse arise on the branches close under the base of the hydrotheeae. The males are 

 reversely conical, with eight short paired spines on the distal part; the narrow distally central aperture 

 has a rudimentary neck, or none at all. 



Material: 



Greenland: Davis Strait 65°22' N., 54°02' W., depth 66 fathoms [Levin sen's type specimen]. 



Diphasia Wandeli appears to be a very rare species; typical three-rowed colonies have, besides 

 the spot mentioned, only been found once, near Papey, East Iceland. All the other specimens recorded 

 by Saemundsson (1902 p. 67 and 191 1 p. 97) belong properly to the above described variety of Di- 

 phasia fallax. The two finds belong to the middle part of the littoral region. 



