HYDROIDA 11 



further data as to the occurrence of the species at West Greenland, where it penetrates right into the 

 Lille Hellefiskebanke. On a single occasion it has been found in Iceland waters. On the coast of 

 Norway it has been met with now and then between Lofoten and Stavanger. It has also been found 

 off Bohuslan (Jaderholm 1909 p. 108). The species belongs to the lower part of the littoral region, 

 and the upper parts of the abyssal. 



Family Aglaopheniidae. 



The hydrothecse are large, with distinctly bilateral structure, sessile, and with the one side 

 wholly or partly fused with the branches. The diaphragma is assymmetrical or bipartite. The polyps 

 can retire altogether into the hydrothecse. The sarcothecse are sessile, immobile and well developed; 

 exceptionally we may find, in addition, also mobile, stalked supracalycine sarcothecse. The hydrotheca 

 margin is as a rule furnished with teeth. The colonies are monopodial with terminal growth point. 

 The endoderm of the polyps is divided into a fore-stomach and a digestive part; the ectoderm often 

 gives off an ectoderm lamella which fastens the polyp to the ribs of the hydrotheca. 



The division of this family is based chiefly upon the nature of the gonangia and the protective 

 formations which are richly and variously developed in the different genera. Primitive in this respect 

 is Halicornaria^ from which the remainder are derived. On the one side, there is a development to- 

 wards Nematocarpus, where the hydrocladia are secondarily branched, though without discernible 

 relation to the gonangia. On the other arise, in all probability separately, the phylactogonia-bearing 

 genera Aglaophenopsis and Cladocarpus, typical deep sea genera, of which the former has hydrotheca- 

 bearing phylactogonia, the latter, on the other hand, only sarcotheca-bearing phylactogonia. Possibly 

 also, the corbula-bearing genera Thecocarpus and Aglaophenia should be derived from these, but their 

 origin is not yet certain. 



Gen. Halicornaria (Busk). 



Upright colonies with branched or unbranched main stem, the apophyses of which bear un- 

 branched hydrocladia with several hydrothecse. All sarcothecse are immobile. The gonangia are situate 

 on the stem or branches without protective organs of any kind. 



Halicornaria campanulata (Ritchie). 

 1912 Cladocarpus (?) campanulatus, Ritchie, Some Northern Hydroid Zoophytes, p. 226. 



The colony is doubly pinnate, with polysiphonic branched main stem, which consists in its 

 extreme portions of the primary segmented tube alone. This has internodia of medium length, which 

 bear about the middle a short, but quite broad apophyse ; the internodium is further provided with 

 a pair of sarcothecse at the upper side of the apophyse, and an unpaired median sarcotheca in front at 

 its lower side; the sarcothecae are almost tubulous, adcaulinally split. The hydrocladia have on each 

 internodium a broad, and not particularly large hydrotheca and three sarcothecse; a supracalycine pair 

 at the opening, and a median proximally, which with its opening margin reaches up to the bottom 



