Some Northern Hydroid Zoophytes. 225 



is distal and posterior. The structure of these individuals is similar to 

 that of the lateral sarcothecse. Two-thirds of the mesial sarcotheca is 

 adnate reaching half way up the hydrotheca ; the remaining free portion 

 is scoop-shaped, and has a crenulated margin. This sarcotheca is longer in 

 our specimen than in Miss Bonnevie's figures. 



No trace of gonosome was found on the specimen. 



Dimensions, 



Stem internode, length 



diameter 



Hydroclade internode, length 



diameter 



Hydrotheca, depth 



0-56 mm. 

 026 mm. 

 0-52—0-58 mm. 

 0-18 mm. 

 0-35 mm. 



diameter at mouth 0*25 mm. 



Locality. — From the neighbourhood of Iceland. 



The only previous record is: lat. 74-55° N, long. 15-49° E., depth 

 373 metres (Bonnevie). 



The consigning of Aglaophenia compressa, Bonnevie, to a definite generic 



position is a matter of some delicacy. Miss Bonnevie slumped all the 



Statoplean Plumularians obtained by the Norwegian North Atlantic 



Expedition under the genus Aglaophenia, but we cannot follow her in this 



simplification. In the separation of the genera of this group, greatest stress 



has been laid upon the gonosome and the arrangements for its protection. 



The present species bears simple gonangia " attached at the base of the 



hydrocladium's first hydrotheca," and this, by itself, would place it in the 



genus Halicomaria, as Broch has indeed done. 1 But besides the unprotected 



gonangia, others are borne on separate conspicuous branches, arising from 



the same place, and bearing nematophores. But they also bear two short 



branches, with hydrothecee, and from the bases of these branches the 



gonangia spring. These seem to represent the simple or branched phylact- 



ogonia, characteristic of genus Cladocarpus, although in the species hitherto 



known hydrotheca? are absent from these protective structures. The 



trophosome helps to resolve the difficulty — for it is more typically 



Cladocarpian than Halicornarian, with its fascicled stem, hydrothecse with 



lateral crenulation and prominent anterior tooth, posterior intrathecal 



ridge, and septal ridges in internodes of hydroclade. We therefore follow 



Jaderholm in transferring the species to Cladocarpus, a proceeding which, 



making Miss Bonnevie's name a synonym, necessitates the adoption of 



1 Broch, "Die Hydroiden der arktischen Meere," in Fauna Artica, Jena, 1909, p. 207, 

 iinder name Halicomaria compressa. 



