Limitation of Genera among the Hydroida. 85l 



Clava leptostyla, Agass. 



Clava diffusa, Allm. 



Clava cornea, Wright. 



Clava membranacea, Wright. 



Clava nodosa, Wright. 



Though the three species, C. cornea, C. membranacea, and C. 

 nodosa are described as Scottish, I have not seen any specimens of 

 them, and I here give them on the authority of Dr. Wright. 



2. TuBicLAVA, AUman. 



Trophosome. — Coenosarc consisting of a well-developed hydro- 

 caulus in the form of simple or branched stems, which are given 

 off at intervals from a creeping filiform hydrorhiza, the wholfe 

 invested by a chitinous periderm. Polypites borne on the 

 summit of the hydrocaulus, claviform, with scattered filiform 

 teutacula. 



Gonosome. — Gonophores adelocodonic, consisting of clusters 

 of sporosacs sessile on the body of the polypite at the proximal 

 side of the tentacula. 



From the above definition the Tubiclava cornucopia of Norman * is 

 excluded, this Hydroid being, in my opinion, the type of a new 

 genus, which is distinguished from Tubiclava by having its gono- 

 phores borne on distinct gonoblastidia, and which, I beUevej Mr. 

 Norman will himself shortly characterize. 



Tubiclava lucerna, Allm. 



3. CAMPANicLAVAf, AUman, nov. gen. 



Trophosome. — Coenosarc a creeping, filiform, ramified hydro- 

 rhiza invested by a periderm ; hydrocaulus undeveloped. Poly- 

 pites sessile on the hydrorhiza, claviform, with scattered filiform 

 tentacula. 



Gonosome. — Gonophores phanerocodonic, sessile on the creep- 

 ing hydrorhiza. Umbrella at the time of its liberation deep bell- 

 shaped ; manubrium simple-mouthed, shorter than the height of 

 the bell-cavity; radiating canals four; marginal tentacles two, 

 continuous with two opposite radiating canals, and having bul- 

 bous bases without distinct ocellus; two intervening smaller 

 bulbs corresponding to the termination of the other two radiating 

 canals in the circular canal. 



There can be no doubt that the Medusa here described undergoes 

 further changes before arriving at maturity. It is, at leasts almost 

 certain that two additional marginal tentacles become developed, 



* See Norman in Ann. and Mag. Nat. Hist. Jan. 1864. . 



t Campana, a bell, and Clava, the name of a genus of Hydroidis. 



