112 



HYDROIDA II 



Diphasia rosacea (Linne) L. Agassiz. ' 

 1758 Sertularia rosacea, Linne, Systema naturae, Ed. 10, p. 807. 



1862 Diphasia rosacea, L,. Agassiz, Contributions to the natural history of the United States, vol. 4, p. 355. 

 Upright colonies without distinct main stem. The colonies are irregularly pinnate or bushily 

 branched, segmented, and with a pair of oppositely placed hydrothecae on each inteniodimn. The 

 hydrothecae are slender, almost evenly tubular, with slightly divergent distal part. The free distal 

 portion of the adcauline wall is about half the length of the hydrotheca, between i l / 2 times and twice 

 the opening diameter, rarely somewhat shorter, down to about the same length as the opening dia- 



too m. _______ 600 on ._._._._. looo m. laoom. 



Fig. LX. The occurrence of Diphasia rosacea in the Northern Atlantic. 

 In the hatched region a common occurrence is recorded. 



meter. The opening margin has a slight adcauline sinus, in which the large opercular plate is attached. 



The gonothecae arise close under the base of the hydrothecae. The males are pear-shaped, 

 with normally eight longitudinal ribs, each terminating in a distal short blunt point; the gonotheca 

 has a central short cylindrical neck. The females are also pear-shaped, with eight long ribs, of which 

 six terminate in as many broad blades closing together over a distal brood-chamber; the two last, 

 diametrically opposite ribs end in forward pointing horn-like outgrowths of varying length. 

 Material : 



"Thor" 633o' N., 2Oi4' W., depth 80 metres. 



Iceland: Stykkisholm, 30 fathoms. 



Saemundsson (1902 p. 66) also mentions specimens of this species from 0nundarfjord, Ice- 

 land, but a reinvestigation of his specimens shows that they must be referred to Diphasia fallax. 



