Report on the Hydroids. 383 



this roof is divided into four free valves by two lines which cross 

 one another, just as is described b\' Levinsen; in the Danmark 

 Expedition's material of Tetrapoma qiiadrideiüatiim (Hincks) I have 

 been so fortunate as to find a young hydrotheca, in the roof of 

 which the two intercrossing lines are visible, corresponding to the 

 four free valves in the still unopened operculum (Plate XXIV, fig. 15). 

 It will have been seen from the above, that there is great diver- 

 sity in the construction of the operculum in this family. 



Synopsis of the northern genera of the family 

 С a m p a n u 1 i n i d a e. 

 Ix The operculum is formed of the upper part 



of the side-wall of the hydrotheca and appears, 



when opened, as a direct continuation of this 2 

 2x The operculum consist of two longitudinally 



folded membranes, which are marked otF from 



the remaining part of the hydrotheca 1эу two 



curves and which on closing run together in 



a fine like a roof Stegopoma Lev. 



2xx Tlie operculum has the form of a many-sided 



pyramid 3 



3x Hydrotheca with distinct, twisted pedicel. Go- 



notheca urceolate or ovate С a m p a n u li n a v. Bened. 



3xx Hydrotheca tutiular without definite pedicel. 



Gonotheca (where known) of the same form 



as the hydrotheca 4 



4x Without nematophores Cuspidella Hincks. 



4xx With nematophores Lafocina Sars. 



Ixx The operculum is formed of the original roof 



of the liydrotheca, marked off from the calycle 



bj' a sharp edge 5 



5x Onl}' the peripheral part of the roof enters 



into the formation of the operculum. The 



closing occurs in the main by folding Calycella (Hincks) Lev. 



5xx The operculum is formed of the whole roof 



and consists of free valves 6 



6x The operculum consists of four valves Tetrapoma Lev. 



6xx The operculum consists of more than four 



valves Lovenella Hincks. 



Genus Stegopoma Levinsen. 

 Stegopoma fastigiatuni (Alder) Levinsen. 

 Campanularia fastigiata Alder 1860 [3] p. 73. PI. V, fig. 1. 



Calycella ,. Hincks 1868 [28] ,. 208. PI. 39, fig. 3. 



Stegopoma fastigiatuni Levinsen 1892 [38] „ 176&180. Tab.VI,Fig.8. 



Jcäderholm 1909 [35] ,, 78, Taf. VIII, Fig. 1. 

 Two hydrothecae on the cirri of Hathrometra (Antedon) proliva 

 (Sladen). The roof-shaped operculum is formed from the upper 

 part of the hydrothecal wall. 



