ATLANT. DEEP-SEA EXPED. 1910. VOL. III. 1 



HYDROIDA 



11 



Fig. 13. Campanu- 

 laria (?) mutabilis 

 from Stat. 37. (X 40). 



Ritchie's colonies, the stalk being a little 

 longer than the hydrotheca, and its 

 middle parts only indistinctly and ir- 

 regularly twisted; near the base, and 

 just below the hydrothecae, the stalk is 

 a regularly spiral. 



Unfortunately both Ritchie's specimens 

 and those taken by the "Michael Sars" 

 are not sufficiently well preserved to 

 allow of any closer examination of the 

 polyp itself, so that we are unable to 

 decide whether this species should really 

 be referred to the Campanulariidae. 



Laomedea Lamouroux. 



Laomedea dichotoma (Lin ) 

 Lamouroux. 



Near Gibraltar (Stat. 20) in 141 metres, a small sterile 

 colony. Near Cape Bojador (Stat. 37) a few sterile colo- 

 nies growing on Nemertesia Hartlaubi from 39 metres. 



Laomedea sargassi nov. nom. {= 

 Clark 1879). 



Obelia hvalina 



Sargasso sea (Stats. 64, 67 and 69) abundant with 

 gonangia on floating sea-weed. 



Sterile colonies of this species cannot be distinguished 

 from Laomedea fruticosa Hincks, and in some cases the 

 gonothecae of both species are so precisely of the same 

 shape, that only their contents enable us to identify the 

 colonies and separate the species. This ought to be a 

 serious obstacle to investigators who try to hide the true 

 relationship among the Campanulariids by dividing them 

 into series of artificial genera merely on account of the 

 contents of their reproductory capsules. 



The shape of the gonothecae of Laomedea sargassi 

 is subject to variations. Sometimes the gonothecae have 

 the shape described by Clark, 1 ) with a broad aperture 

 stretching across the entire, square, distal end, but in most 

 cases they have the same shape as in our common re- 

 presentatives of the Obelia-group: Laomedea geniculata 

 (Lin.), Laomedea longissima (Pallas), and Laomedea dicho- 

 toma (Lin.), the terminal part being provided with a short 

 neck and with a narrow orifice, which occupies only one- 

 third to one-half of the distal diameter of the capsule. 

 Clark found only gonongia twice, the length of the hydro- 

 thecae, but in the "Michael Sars" material they are often 

 three times the length of the hydrothecae, or even a 

 little more. 



The name Laomedea hyalina being employed for a 

 species belonging to the Gonothyraea-gmup, I have 

 proposed the name Laomedea sargassi. 



Laomedea bifurca (Hincks)? 



A small sterile colony from 141 metres west of Gi- 

 braltar (Stat. 20) seems to belong to this species. 



II. Remarks on geographical distribution. 



The collections from the cruise of the "Michael Sars" 

 in 1910 include representatives of two natural biological 

 groups, namely hydroids from the bottom, and hydroids 

 from floating sea-weed. 



Hydroids From The Bottom were taken in 

 the eastern parts of the Atlantic, partly a little to the 

 west of Gibraltar, partly between Cape Bojador and the 

 Canaries. Hydroids were met with at few stations; but 

 in some of the catches they were very abundant. 



Near Gibraltar the following species were obtained: 

 Plumularia setacea. 

 Antenella secundaria. 

 Nemertesia ramosa. 

 Thecocarpus myriophyllum. 

 Cladocarpus (?) Hjorti. 

 Grammaria conferta. 

 Diphasia pinaster. 

 Laomedea dichotoma. 

 All these species except two {Grammaria conferta and 

 Cladocarpus Hjorti) have been met with in the Mediter- 

 ranean. Grammaria conferta is a typical deep-sea hydroid. 

 Two exceedingly rich hydroid localities were investi- 

 gated near Cape Bojador, one in 39, the other in 77 

 metres, the following species being obtained: 

 Perigonimus Jonesi. 

 Antenella secundaria. 

 Nemertesia ramosa. 

 Hartlaubi. 

 rugosaP 

 Aglaophenia dichotoma. 

 sept if era. 

 tubulifera. 

 Thecocarpus myriophyllum. 

 Grammaria serpens. 

 Sertularella cylindritheca. 

 Campanularia Hincksi. 



(?) mutabilis. 

 Laomedea dichotoma. 

 bifurca? 



*) Reports on the Dredging OperaHons of the U. S. Coast Survey Steamer ''Blake". 

 Vol. V) Cambridge Mass. 1879, p. 241, pi. IV, fig. 21. 



III. Report on Hydroida (Bull. Mus. Comp. Zool. 



