Limitatian of Genera among the Hydroida. 359 



2. AcHABADRiA, StrcthiU Wright. 



Trophosome. — Hydrocaulus branched, with a well-developed 

 periderm ; hydrorhiza (?). Polypites with two verticils of tenta- 

 cula, those composing the proximal verticil long and filiform, 

 those composing the distal verticil short and capitate. 



Gonosome unknown. 



Acharadria larynx, Wright. 



3. Heteractis*, AUman, nov. gen. 



TVophosome. — Polypite solitary, borne on the summit of a 

 simple rooted hydrocaulus ; two verticils of tentacles, a proximal 

 and a distal, — the tentacles composing the proximal verticil long 

 and " annulated " (Sars), those composing the distal verticil short 

 and capitate. 



Gonosome. — Gonophores phanerocodonic, borne upon pedun- 

 cles, which arise from the body of the polypite at the distal side 

 of the proximal verticil of tentacles. Umbrella in the form of a 

 shallow bell, with four radiating canals, one large marginal 

 tentacle, and three rudimental ones. 



The genus Heteractis is constructed for the Corymorpha annuli- 

 cornis of Sars, which is certainly not a Corymorpha, as indeed Sars 

 himself suspects ; it may possibly belong to the genus Vorticlava, Alder, 

 as already suggested by Hincks ; but, from our present knowledge 

 of it, and the absence of all knowledge of the gonosome in Vorti- 

 clava, we should hardly yet be justified in associating the two forms in 

 a common genus. 



Heteractis annulicornis, Sars (sp.), = Corymorpha'^ annulicornis, 

 Sars. 



4. Stauridium, Dujardin. 



Trophosome. — Coenosarc consisting of a branched or simple 

 hydrocaulus arising from a creeping filiform hydrorhiza, the 

 whole invested by a periderm. Polypites borne on the summits 

 of the hydrocaulus, clavate, with two verticils of tentacles, each 

 verticil consisting of four tentacles arranged in a cross; the 

 tentacles of the proximal verticil filiform, those of the distal 

 verticil capitate. 



Gonosome. — Gonophores phanerocodonic, developed from the 

 body of the polypite. Umbrella deep bell- shaped ; manubrium 

 not reaching the margin of the bell ; mouth simple ; radiating 

 canals four ; marginal tentacles four, nodulated with clusters of 

 thread-cells, and with a distinct ocellus on the basal bulb f. 



The name Stauridium is the same as " Stauridie " of Dujardin, 



* From erepos, dissimilar, and uktis, a ray. 



t Hincks has pointed out the identity in every respect of the gonophore 

 of Stauridium productum with that of Coryne (Syncoryne) eximia. 



