778 SOME NEW AND RARE HYDROIDA IN THE AUSTRALIAN MUSEUM, 



PLUMULARIA RUBRA, von Lendenfeld. 

 (Plate XX., figs. 1-6). 



Hydrocaulus about three inches high, stems clustered, raonosi- 

 phonic, unbranched, bearing hydrothecae as well as pinnae. Pinnae 

 alternate, distant, one on each internode, often supporting 

 secondary hydrocladia, joints oblique, a hydrotheca on each inter- 

 node, except the first on each pinna. Hydrothecsa borne at the 

 lower ends of the internodes, set at an angle of about 40, large, 

 campanulate, margin entire, free at the back. Sarcothecae 

 bithalamic, canaliculate, fixed and stout at the base ; one at each 

 side of the hydrotheca, pedunculate, one in front, one (or on the 

 stem two) midway between every two hydrothecae, on the same 

 internode as the lower, and one on the proximal internode of 

 each pinna. 



Gonothecse female, large, pear-shaped, somewhat flattened 

 above, tapering below, with a distinct sub-globular segment at 

 the base of the capsule, and a sarcotheca at each side a little 

 above the base ; a circular operculum at the summit, the border 

 of the aperture slightly thickened : male, small, with one sarco- 

 theca only ; both sexes on the same shoot. 



Hob. Port Jackson. 



The minute structure of this species is identical in every 

 particular with that of P. campanula, both as regards the tropho- 

 some and the gonosoine ; but in P. campanula the pinnate 

 branches are borne by a polysiphoiiic stem, while in P. rubra 

 the pinnate shoots spring directly from the hydrorhiza. A stem 

 of P. rubra therefore corresponds to a branch of P. campanula, 

 except that it is usually larger. 



PLUMULARIA SETACEA, Ellis. 

 P. tripartita, von Lendenfeld. 



(Plate XX., figs. 14-18). 



Hydrocaulus about 1J inches in height, monosiphonic, some- 

 times branched, pinnae alternate, not close, one borne near the 



