_. 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 le.ss than 5.6=; it is thus not impo.ssible 

 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 Aglaopheniid hitherto found in any number in arctic 

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

 the Aglnnphrniida- on the whole as southern visitors in the colder northern seas. Halicornaria cavi- 

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



Nematocarpus nov. gen. 



Singh- or doubh- pinnate colonies, the apophyses of the primary stem tubes bearing hydrocladia, 

 which in fullv developed colonies are secondarily branched. All sarcothecce immobile. The secondary 

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

 to the gonangia. Tlie latter are not surrounded b\- any protective organs. 



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

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

 not branched; hydrocladia] internodes without septa". The latter point is of minor importance even 

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

 "Hydrocladien einfach". 



On the other hand, we ma\' with some justification maintain that the genus Aglaopliciiopsis 

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

 ence in comparison with Halicornaria ramulifera AUmau; the secondary branches in Aglaophenopsis 

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

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

 Aglaophenopsis, but into secondary lu'drocladia of the same structure and appearance as the primar\'. 

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

 new genus on the basis of the same. Tlie nearest related genera are Hnliconiaria, Aglaoplu-iiopsis, 

 and Cladocarpus, where we often, especialh' in the two last, find the same structure of the gonotheca 

 as in the known Ni'iiKitonirpiis s])ecies. 



Nematocarpus ramuliferus (Allman). 



1874 Halicornaria ramulip'era, Allman, Report on the Hydroida Porcupine, p. 477, pi. 67, fig. 3. 



1903 Halicornaria pli( ma, Broch, Die von dem norwegischen Fischereidampfer "Michael Sar.s" 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 sarcothecae at the upper .side of the apophvse; the sarcothec;e 



are adcaulinally split. From the apophyse proceeds a hydrocladium, bearing a h>-drotheca on each 



