io 6 HYDROIDA II 



Sertularella fusiformis assumes a highly characteristic appearance from the peculiarity that it 

 has often on stem or branches two or three short branchlets proceeding simultaneously from the same 

 point, these short branchlets consisting of a single interuodium, or more rarely a couple, with large 

 hydrothecse almost terminally placed. An excellent picture of this is given by Jaderholm (1909 Taf. 

 11, fig. 9). His specimens undoubtedly belong to Sertularella fusiformis, and are only remarkable in 

 having the internodia entirely smooth; here, however, all transition stages occur, so that we are not 

 warranted in setting aside the specimens on such ground as tvpes of a distinct species. 



Sertularella fusiformis is probably a warm atlantic species, but its occurrence is little known. 

 In the waters investigated, it is previously known from the Hebrides, and from the Clyde Sea area; 

 to these, Jaderholm adds a single find from Spitzbergeu, and the species has now also been taken 

 by the "Iugolf" about midway between the Faroe Islands and Iceland. 



Sertularella rugosa (Linne) Hincks. 



1758 Sertularia rugosa, Linne. Systema naturae, Ed. 10, p. 809. 



1868 Sertularella rugosa, Hincks, A History of the British Hydroid Zoophytes, p. 241, pi. 47, fig. 2. 



Upright, irregularly branched small colonies without pronounced main stem; the latter is mono- 

 siphonic. The colony is divided by oblique nodes into short internodia, each bearing a hydrotheca 

 directed alternately to either side, and situate 011 the upper half of the interuodium. The hydrothecse 

 are broad oval or barrel-shaped, with deep transverse furrows, which are particularly marked on the 

 abcauline side, where a very deep furrow is always found immediately beneath the aperture. The 

 opening forms an angle with the hydrotheca axis, and is turned away from the branch; it is furnished 

 with four low, often somewhat indistinct teeth, between which four triangular lid plates are attached. 

 The polyp has a large abcauline blind sack. 



The gonothecae proceed from the internodia close under the hydrothecse. 

 They are egg-shaped or more oval, with deep transverse furrows, and have distally 

 a central broad opening, surrounded by four short strong teeth. 



Material : 



Jan Mayen, depth 15 fathoms (East Greenland expedition). 

 Iceland: Grindavik (depth not stated) 



10 miles W. of Akranes, on algse 

 Stykkisholm, depth 30 fathoms 

 Bredebugt (without further details) 

 Fig. lvii. Hydrotheca;. The F aroe Islands: Solmunde, on algse 



of Sertularella rugosa Thorshavii, on algse, depth 3—4 fathoms. 



from Herlo near Bergen 



(X40). Vestmanhavn, — 3,5-4 



The available illustrations of Sertularella rugosa are very little characteristic, and this applies 

 especially to Nutting's (1904 pi. 17, figs. 1 — 5) which present an entirely misleading impression, in- 

 asmuch as they suggest that the hydrotheca; are distinctly ringed. A new drawing is therefore given 

 here (fig. LVII) showing the deep transverse furrows; particularly characteristic is the deep abcauline 

 furrow beneath the aperture. 



