HYDROIDA II 



that we have to deal with a form from the warmer Atlantic regions; both the finds are in fact from 

 near the north coast of Iceland. At the same time, however, it should be noted that both are situate 

 in water of positive temperature; at the "Ingolf" St. 127 no less than 5. 6°; it is thus not impossible 

 that the occurrence of the species here is due to larval transportation from the Danmark Strait. Arctic 

 the species certainly cannot be; even the one Aglaoplicniid hitherto found in any number in arctic 

 water lavers, Thecocarpus myriophyllum (Linne) is not indigenous there. We must therefore regard 

 the Aglaopheniidce on the whole as southern visitors in the colder northern seas. Halicornaria cam- 

 panula fa must likewise be placed in this category; its true home, however, has yet to be discovered. 



Nematocarpus nov. gen. 



Singly or doubly pinnate colonies, the apophyses of the primary stem tubes bearing hydrocladia, 

 which in fully developed colonies are secondarily branched. All' sarcothecse immobile. The secondary 

 hydrocladium is formed from the proximal sarcotheca branch on the primary, and stands in no relation 

 to the gonangia. The latter are not surrounded by any protective organs. 



This peculiar genus is known only in a single species, originally described as a Halicornaria 

 by Allman (1874 p. 477). In Nutting's diagnosis of this genus (1900 p. 126) we find "Hydrocladia 

 not branched; hydrocladial iuternodes without septa". The latter point is of minor importance even 

 in distinction of species, but the first-mentioned character is also adopted by Stechow (1913 p. 43) 

 "Hydrocladien einfach". 



On the other hand, we may with some justification maintain that the genus Aglaophcnopsis 

 (Fewkes) is based on forms with branched hydrocladia. We must, however, here note a great differ- 

 ence in comparison with Halicornaria ramulifera Allman; the secondary branches in Aglaopkenopsis 

 are hydrotheca-bearing phylactogonia, and stand thus in definite relation to the gonangia; in this case, 

 however, they have nothing to do with the gonangia, and do not develope into minor branches, as in 

 . Iglaophenopsis, but into secondary hydrocladia of the same structure and appearance as the primary. 

 This difference is important, inasmuch as we should, as Bale already (1887) pointed out, establish a 

 new genus on the basis of the same. The nearest related genera are Halicornaria, Aglaopkenopsis, 

 and Clailocarpus, where we often, especially in the two last, find the same structure of the gonotheca 

 as in the known Nematocarpus species. 



Nematocarpus ramuliferus (Allman). 



1S74 Halicornaria ramulifera, Allman, Report on the Hydroida .... Porcupine, p. 477, pi. 67, fig. 3. 

 1903 Halicornaria pin ma, Broch, Die von dem norwegischen Fischereidampfer "Michael Sars" .... ge- 



sammelten Hydroiden, p. 8, Taf. IV, figs. 15—21. 



Doubly pinnate colonies, with somewhat irregularly branched, polysiphonic main stem. The 



primary tube is segmented, and has on the middle of each internodium a strong apophyse, directed 



alternately to each side, and a pair of sarcothecse at the upper side of the apophyse; the sarcothecse 



are adcaulinally split. From the apophyse proceeds a hvdrocladium, bearing a hydrotheca on each 



