IV. ADDENDUM TO THE AUSTRALIAN ' 

 HYDROMEDUS^. 



HYDRA HEXACTINELLA. Nova Species. 



Plate XLVITI., Fig. 1-4. 



By R. von Lendenfeld, Ph.D. 



In my paper, Monograph of the Australian Hydromedusse, 

 Part III. (Vol. IX., page 345 of these Proceedings), I mentioned 

 three species as the Australian representatives of the genus Hydra. 

 I found afterwards that the specimens described as distinct, under 

 the names of Hydra oligactis and Hydra fusca respectively, are 

 identical, and I place these in my amended catalogue (Zeitschrift 

 fiir wissenschaftliche Zoologie, Band XLT., Seite 627) in the first 

 species Hydra oligactis, Pallas, The reasons for this are given in 

 the first Addendum to the Australian Hydromedusse (Vol. IX., 

 page 908, of these Proceedings.) 



In Australasia we accordingly find the genus Hydra I'epresented 

 by two species : — 



1. Hydra oligactis, Pallas, Victoria, 



2. Hydra viridis, Linne, New Zealand. 



To these two, a third species from New South Wales must now 

 be added, which brings the total number of Australian species 

 belonging to this order, up to 255, 



HYDRA HEXACTINELLA. Nova Species. 



This species can be distinguished ^rom all other Hydras by the 



constancy in the number of arms, which is invariably six. These 



tentacles are all equal in length and thickness, and the angles 



between them are perfectly equal, measuring 60°. Such a 



