258 MERONA CORNUCOPIA. 



GONOSOME. — ^Sporosacs borne on blastosttles, which spring directly from 

 the creeping hydrorhiza. 



This genus has been instituted by the Rev. A. Merle Xorman, for the reception of a hydroid 

 which he at first referred to the genus Tubiclava. The gonosome, however, belongs to a type 

 generically different from tliat which we have reason to believe is the gonosome of Tubiclava, for 

 while in the latter genus the gonophores would seem to be borne directly by the hydrautb, they 

 are in Merona carried upon blastostyles which spring from the hydrorhiza. 



Merona coENUcoPLffl, Norwian. 



Tubiclava coRNUcopiiE, — Norman, in Ann. Nat. Hist., for Jan., 1864, pi. ix, fig. 5. Hincks, 



Brit. Hydr. Zooph., p. ii, pi. ii, fig. 2. 

 Merona cornucopia, — Norman, Ann. Nat. Hist., for April, 1865. 



TROPHOSOME. — Htdrocaulus consisting of shghtly curved trumpet-shaped 

 tubes, which are given off at short intervals from the creeping hydrorhiza, and 

 gradually increasing in diameter from the base to the summit, attain a height of one 

 fifth of an inch, or a little more, the tubes marked by a few slightly elevated trans- 

 verse lines of periodic growth. Htdranths with greatly elongated club-shaped 

 heads, 



GONOSOME. — Gonophores forming mulberry-like masses on the summit of 

 very short blastostyles, which are invested at their base by a tubular extension of the 

 hydrorhizal perisarc. 



Habitat. — Growing on the shells of living mollusca from deep water. 

 Bathymetrical distribution. — Deep sea zone. 



Localifi/. — About twenty miles north of Unst in Shetland, Rev. A. M. Norman. Other 

 parts of the Shetland seas, Mr. Peach. 



Merona cormicopice was observed by j\Ir. Norman upon the shells of Astarte sulcata and 

 Dentalium entails which had been dredged from a depth of from SO to 100 fathoms. The very 

 considerable depth thus frequented by this hydroid constitutes an interesting fact in its economy. 

 Mr. Norman also informs us "that in every instance it was observed upon shells still occupied 

 by the living mollusca, and that it had invariably assumed a position at the posterior extremity 

 of the shell where it would receive the benefits of the aqueous currents caused by the mollusc." 



