Limitation of Genera among the Hydroida. 373 



3. Laomedea, Lamouroux (in part). 



Trophosome. — Hydrocaulus simple or branched, rooted by a 

 creeping filiform hydrorhiza; hydrotbecse bell-shaped, with the 

 margin entire or serrated, but without an operculum ; tentacular 

 verticil surrounding the base of a very contractile, conical or 

 trumpet-shaped metastome. 



Gonosome. — Gonangia developed on the hydrorhiza or hydro- 

 caulus, and containing adelocodonic gonophores, which never 

 leave the cavity of the gonangium. 



English authors generally include under Laomedea those species 

 of CampanularidcB which are furnished with a branching hydrocaulus, 

 while they refer to Campanularia those in which the hydrocaulus is 

 simple. No generic distinction, however, can be based on this cha- 

 racter — a character really unimportant, and frequently so little com- 

 prehensive that we may find the two conditions combined in the 

 same species, thus rendering caution necessary in the employment of 

 this character, even for the purposes of specific diagnosis. 



It will be at once apparent from the diagnoses here given of Cam- 

 panularia, Obelia, and Laomedea, that the differences in the gono- 

 somes afford excellent characters by which we can distribute between 

 three perfectly natural genera numerous forms of CampanularidcB 

 which would otherwise defy our attempts at a satisfactory classifica- 

 tion. 



* Plydrocaulus mostly branched. 



Laomedea flexuosa, Hincks (sp.),= Laomedea gelatinosa, var. a, 

 John St. 



Laomedea neglecta, Alder. 



Laomedea angulata, Hincks. 



Laomedea amphora, Agass. 



Laomedea exigua, Sars. 



Laomedea decipiens, Wright. 



** Hydrocaulus mostly simple. 



Laomedea volubiliformis, Sars (sp.), = Campanularia voluhili- 

 formis, Sars. 



Laomedea poterium, Agass. (sp.), = Clytia poterium, Agass. 



Laomedea caliculata, Hincks {%^.) ,■=■ Campanularia caliculata, 

 Hincks. 



4. HiNCKSiA, Agassiz. 



Trophosome. — Hydrorhiza a creeping network of filiform 

 tubes, from which a short simple hydrocaulus is emitted at in- 

 tervals; hydrothecse bell-shaped, destitute of operculum. Po- 

 lypites ? 



Gonosome. — Gonangia borne on the hydrorhiza, and consist- 

 ing of large, subcordate, pedunculated capsules with a small 

 terminal aperture, transversely ribbed on one side, smooth on 

 the other. 



