766 SOME NEW AND RARE IIYDROIDA IN THE AUSTRALIAN MUSEUM, 



length, each bearing a hydrotheca on its upper part. Hydrothecai 

 adnata nearly half their height, large, stout, cylindrical, smooth, 

 usually somewhat rounded at the base, curved outwards ; aperture 

 looking outwards and upwards, not contracted, margin entire, 

 very slightly everted, peristome often double or triple. 



Gonothecpe unknown. 



Hah. — Port Jackson. 



A single specimen occurred among a mass of S. divaricata var. 

 suh-dicJioioma. It is quite unlike any Australian species hitherto 

 known, and may be readily distinguished by the uncontracted 

 entix^e margins of the hydrothecae. The latter somewhat resemble 

 those of Sertularia patula, Busk, but ai-e free for a much greater 

 portion of their length. I could not satisfy myself of the exist- 

 ence of an operculum. 



Synthecium, Allman. 



The genus Synthecium differs from Sertularia in the gonosome, 

 the pedicels of the gonangia having their origin within certain of 

 the hydrothecse, where they take the place of the hydranths. The 

 Sertularia orthogonia of Busk, the gonosome of which has hitherto 

 been unknown, belongs to this genus, so also doubtless does 

 .S'. patula. The Dyuaniena tubulosa, Heller (Zoophyten und 

 Echinodermeu des Adriatischen Meeres), is evidently a Synthe- 

 cium. Professor Allman has remarked that Heller's figure shows 

 a gouaugium sjn-inging directly from the stem, but I have no doubt 

 that what Heller has figured is a parasitic hydroid like Campan- 

 nularia (?) costata. 



The five known species all agree in having opposite pinnie, 

 which spring from the stem at a point where there are no hydro- 

 thecae, also in having the liydrothecse opposite, tubular, curved 

 outwards, and with the margin entire. Professor Allman's two 

 species ( which are probably reducible to one) have the hydvothecse 

 veiy much slenderer in proportion to the length than S. orthogonia 

 and S. patula (which may perhaps be also united). Heller's 

 species is likewise very similar to <S'. patula, aud may be identical. 



