Prof. Allman on the Hydroida. 59 



imperfect verticil of three or more. Between the medasa of the 

 various species of Bougaitivillia whose trophosome has been 

 obsen-ed I cannot discover any difference which could be ad- 

 vantageously employed in the diagnosis. 



Heterocobdvlk, Allman *. 



Gen. char. : Trophoiome. — CoBnosarc consisting of a simple or 

 branched hydrocaulus, which arities from a creeping filiform and 

 anastomosing hydrorhiza, the whole invested by a chitinous peri- 

 derm. Polypites fusiform, with a single verticil of filiform ten- 

 tacula round the base of a conical metastome. 



Gonosome, — Gonophores adelocodonic, borne by gonoblastidia 

 which are developed (solely ?) from the hydrorhixa ; sporosacs in 

 the form of simple fixed sacs destitute of tentacles and cilia. 



Species unica : H. Conybearei, Allman. Plate II. 



Trophoiome. — Hydrocaulus consisting of numerous much- 

 branched stems, along with short simple ones, all crowded on the 

 creeping hydrorhiza, the longest stems attaining a height of 

 about four lines; periderm transversely corrugated, sUghtly 

 dilated at the base of the polypites, ash-brown. Polypites with 

 about twelve tcntacula, usually held straight on extension, with 

 the alternate ones depressed when partially contracted, the tenta- 

 cles present a slightly clavate outline at tLeir extremities. 



Gonosome. — G<xioblastidium springing out of a short tubular 

 process from the upper surface of the hydrorhiza, club-shaped, 

 its distal extremity thickly set with thread-cells; gonc^hores 

 numerous, on very short peduncles, densely crowded, commen- 

 cing a little behind the distal extremity of the gonoblastidium, 

 and thence extending to within a short distance of its base. 



H. Conybearei was obtained last autumn in considerable abun- 

 dance in the Harbour of Glengariff, co. Cork, investing old 

 univalve shells which had been taken possession of by hermit 

 crabs. In habit it exactly resembles Dicoryne ooi^ertay and with- 

 out the aid of a microscope might be easily mistaken for this 

 species ; but the structure of the gonophores, which are simple 

 sporosacs, entirely resembling those of Clata, must remove it by 

 a wide inter\al from Dicoryne. 



I have much pleasure in calling the present species after an 

 ardent and scientific worker with the microscope, a member 

 of a family whose name is already inseparably united with the 

 progress cj natural science in these islands, Henry Conybeare, 

 Esq., in whose company, during a dredging-expedition in the 



* I have already given in the Synopsis a diagnosis of this genus, unac- 

 companied, however, by a figure or by a deaoiption of the only known 

 ipeaes. 



