266 PROP. ALLMAN ON NEW GENEEA 



Synthecium elegans. Plate XV. figs. 1-3. 



Tropliosome. Hydrocaulus attains a height of about 2 inches, 

 springing from a creeping tubular filament and soon sending off 

 opposite pinnately arranged branches ; intemodes separated from 

 one another by a deep constriction. Hydrothecse borne along 

 both the main stem and its branches, deep, tubular, cylindrical, 

 with perfectly even orifice, adnate to the internode for about two 

 thirds of their height, and then becoming free and curving out- 

 wards. 



Gonosome. Gonangia large, elliptical, opening on the summit by 

 a tubular orifice, strongly annulated, with the annular ridges, 

 discontinuous, where they nieet a mesial zigzag line on the front 

 and the back of the gonangium, peduncle of gonangium entirely 

 concealed within the hydrotheca which encloses it. 



Locality. New Zealand," Jir. BusFs collection. 



I have elsewhere* given a general description of this remark- 

 able hydroid, bnt without the technical diagnosis which I have 

 here supplied. It is a beautiful little species, rendered striking 

 by the regularity of its ramification, its distinctly separated per- 

 fectly symmetrical pairs of hydrothecse and its large curiously 

 ornamented gonangia borne in pairs corresponding to those of the 

 hydrothecae out of which they spring. 



The peduncle of the gonangium nearly fills the cavity of the 

 long tubular hydrotheca, from the very bottom of which it springs. 

 It is covered with a delicate chitinous perisarc, and immediately 

 on emerging from the cavity of the hydrotheca carries the gonan- 

 gium on its summit. Its ccenosarc is doubtless continuous at 

 the bottom of the hydrotheca with that of the common stem ; but 

 as the specimens examined had all been dried before I received 

 them, the exact relation of the soft parts could not be determined. 



In the dried trophosome itself there is nothing exceptional. 

 Indeed, so far as this part of the hydroid is concerned, there is 

 nothing which would separate it generically from a typical Ser- 

 tularia. 



Whether those hydrothecse from which the peduncles of the 

 gonangia emerge ever carried hydranths which subsequently be- 

 came replaced by the gonosome, or whether they have been all 

 along exclusively devoted to the gonosome, it is impossible to de- 

 termine from dead and desiccated specimens. 



* ' Gymnoblastic Hydroids,' p. 229. 



