356 TUBICLAVA LUCERNA. 



Some time afterwards I obtained at Tenby another hydroid resembling the Torquay one in 

 all its more important charactere, but with a still more conspicuous hydrocaulus, for this was 

 occasionally branched, while it attained at least twice the height of that of the hydroid from 

 Torquay. Like this, however, the Tenby hydroid was unfortunately without a trace of 

 gonosome. 



From a comparison of the three hydroids now mentioned, I consider myself justified for the 

 present in regarding the Tenby and Torquay hydroids as generically identical, though specifically 

 distinct, while that from Dublin Bay is probably of the same species as the Torquay one. 



It is to the new genus thus represented by two species that I have given the name of 

 Tubiclava; but since I do not at this distance of time feel absolutely certain as to the identity 

 of the Dublin Bay and Torquay hydroids, the gonosome of Tubiclava must still be regarded as in 

 some respects hypothetical, and the genus itself as defined above must be accepted with just 

 so much of a provisional element. 



If the gonosome of Tubiclava be formed as here considered probable on the type of that of 

 Clava, then Tubiclava is a Clava with a developed hydrocaulus, and is especially interesting as 

 a transition form between Clava and Cordylophora, its gonosome being that of the former, and its 

 trophosome that of the latter. 



1. Tubiclava luceena, Allman. 

 Plate IT, figs. 7, 8. 

 Tubiclava lucerna, — Allman. la Ann. Nat. Hist., for June, 1863, and for May, 1864. 



TROPHOSOME. — Hydrocaulus about two lines in height, sinii)le, cyhndrical, 

 with a slight dilatation at the base of the hydranth ; perisarc with shallow corruga- 

 tions. Htdranth when extended about equal in height to the stem, and with about 

 twenty tentacles, which are confined to its distal third. 



GONOSOME. — [GoNOPUOREs in dense clusters, immediately below the proximal 

 tentacles.] ?^ 



Colour. — Hydranths milk white, with pale ochreous tint on the stomach cavity. 

 Development of Gonosome. — (?) observed in June. 

 Habitat. — Creeping over stones in rock pools. 

 Batliymetrical distribution. — Litoral zone. 

 Localities. — Dublin Bay and Torquay, G. J. A. 



Tubiclava lucerna is a minute hydroid, and might easily be overlooked or without close 

 examination be mistaken for a creeping form of Clam. The hydranth is very contractile ; when 



^ See for tlie evidence as to the nature of the gonosome the general remarks on the gen\is given 

 above. 



