Limitation of Genera among the Hydroida. 359 
2. AcHarapRia, Strethill 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. 
8. Hereractis*, Allman, noy. gen. 
Trophosome.—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, Sravripium, Dujardin. 
Trophosome.—Ccenosare 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 buibf. 
The name Stauridium is the same as “Stauridie” of Dujardin, 
* From €repos, dissimilar, and axris, a ray. 
+ Hincks has pointed out the identity in every respect of the gonophore 
of Stawridium productum with that of Coryne (Syncoryne) eximia. 
