286 Transactions. — Zoology. 



." It is a typical Sertularian whose gonosome presents the hitherto 

 unprecedented character of having its gonangia borne on peduncles which 

 spring from within the hydrothecEe. 



" The gonangia are oval, opening at their distal extremity by a tubular 

 orifice and ornamented by curved ridges, which terminate at each side in a 

 zigzag line, which runs down the middle of the gonangium walls from the 

 summit to the base. Each gonangium is borne on a long cylindrical peduncle 

 which springs from the bottom of a hydrotheca, in which it occupies the position 

 of a hydranth. 



" The peduncle extends through the whole length of the hydrotheca, and 

 as it nearly equals it in diameter, it almost fills its cavity. It is covered by a 

 delicate chitinous perisarc, and immediately on emerging from the cavity of 

 the hydrotheca carries the gonangium on its summit. 



" Whether those hydrothecse from which the peduncles of the gonangia 

 emerge ever carried hydranths, which subsequently became replaced by the 

 gonosome, or whether they have been all along exclusively devoted to the 

 gonosome, it is impossible to determine from dead and desiccated specimens. 



" At all events it is certain that there is not a single point either in 

 position or in form by which these gonangia-bearing hydrotheca? differ from 

 the others. 



" The hydroid thus is very exceptionally constructed and must constitute 

 the type of a new genus and species to which the name of Synthecium 

 elegans may be given."* 



In a specimen of this obtained among other objects on the oyster beds at 

 Stewart Island I had not the good fortune to discover any gonangia, but it 

 enables me to add to the above description. Hydrocaulis short and dichoto- 

 mously divided. Hydrothecte tubular, smooth, curved outwards, aperture 

 entire, a marked constriction in hydrocaulis between each pair of hydrothecse. 

 Professor Allman does not give the special part of New Zealand from which 

 Mr. Busk's specimen was obtained ; I am indebted for the Stewart Island 

 specimens to Mr. Street. Figs. 24 and 25. 



Synthecium gracilis, sp. no v. 



Hydrophyton consisting of very small branches growing from a creeping 

 hydrorhiza ; pale brown in colour. 



Hydrorhiza delicate, filiform, open, network creeping over fronds of 

 delicate seaweeds, sending up branches to the height of one-eighth or one- 

 fourth of an inch-seldom higher. Branches markedly erect, simple, highest 

 having only about ten pairs of hydrotheca*, majority only about seven pairs, 

 terminating in a slight tumescence at open angle between distal pair of 



G. J. Allman, Gyumoblaatic Hydroids, p. 229. 





