Limitation of Genera among the Hydroida. 375 



sibility of the polypites, and their power of complete retraction into 

 hydrotheca-Uke receptacles, would seem to indicate that the affinities 

 of Trichydra are rather with the Campanularian than with the 

 Tubularian Hydroids. 



JVichydra pudica, Wright. 



7. Calycella, Hincks. 



Trophosome. — Hydrocaulus erect, and rooted by a filiform 

 hydrorhiza, or creeping and adherent ; hydrotheese tubular or 

 conical, and provided with an operculum which is formed of 

 converging lanceolate segments. Polypites cylindrical, with the 

 tentacular verticil surrounding the base of a conical metastome. 



Gonosome. — Gonophores adelocodonic. Sporosacs of female 

 ultimately delivering their contents into an acrocyst. 



The genus Calycella was founded by Hincks (Ann. Nat. Hist. 

 Oct. 1861) with the intention of including under it certain Hydroids 

 previously placed under Campanularia and Laomedea. Calycella, 

 however, as constructed by Hincks, really involves two distinct types, 

 one of these being represented by Calycella dumosa, Hincks (gen.), 

 and the other by Calycella syringa, Hincks (gen.). 



Now the C. dumosa belongs to a form which had been already 

 defined by Lamouroux under the name of Lafoea, a name, therefore, 

 which the rule of priority obliges us to leave undisturbed ; and the 

 name of Calycella must accordingly be retained for the remaining 

 type alone — that represented by the Campanularia syringa of au- 

 thors, and by the Campanularia lacerata of Johnston. 



Calycella syringa, Linn. {sp.), = Campanularia syringa, Lamk., 

 = Clytia syringa, Lamx., = Campanularia syringa, Van Ben., = 

 Wrightia syringa, Agass. 



Calycella lacerata, Johnst. (sp.), = Campanularia lacerata, 

 Johnst;.,= Wrightia lacerata, Agass. 



Calycella? humilis, Hincks. 



8. Campanulina, Van Beneden. 



Trophosome. — Hydrocaulus branching or simple, attached by 

 a creeping filiform hydrorhiza ; hydrothecse with their margin 

 continued by a delicate collapsible membrane [or else provided 

 with a true operculum formed by converging lanceolate seg- 

 ments]. Polypites cylindrical; tentacula connected by a mem- 

 branous web at their base. 



Gonosome. — Gonophores phanerocodonic. Medusa, at the time 

 of liberation, deep bell- shaped, with moderate-sized four-lipped 

 manubrium ; radiating canals four, each terminating distally in 

 a non-ocellated bulb ; marginal tentacles two, developed from two 

 opposite bulbs [or four, every bulb then carrying a tentacle] ; 

 lithocysts eight, two in each interradial marginal space. 



