ARTICLE IV. — A New Family of Hydeoidea, together with a Description 

 OF the Structuee of a New Species of Pldmolaria, by W. Baldwin Spencer, 

 M.A., Professor of Biology in the University of Melbourne. 



(Read Nov. 12th, 1890.) 



The following deals with two hydroid forms obtained by Mr. J. Bracebridge 

 Wilson, M.A., from the neighbourhood of Port Phillip. One of these is so distinct 

 from any hitherto described that it must be taken as the type of a new Family, to 

 which the name of Hydroceratinidfe is given, the other is a new and somewhat 

 curious species of the genus Plumularia. The paper is, therefore, divided into two 

 parts — (1) On the Hydroceratinidae, a new family of the order Hydroidea, and (2) On 

 Plumularia procumbens, a new species of the genus Plumularia. 



(1) On the Hydroceratinid^, a New Family of the Order Hydroidea. 



The form in question undoubtedly calls to mind, in the general appearance of 

 the dried specimens, one of the two genera which were placed in a distinct family — 

 the Ceratelladae — by Dr. Gray,* and, when this paper was read before the Eoyal 

 Society of Victoria, I provisionally referred it to this family, f Dr. Gray had doubtfully 



f Note. — Up to the time of reading this paper I had only the necessarily 

 somewhat imperfect descriptions (since taken from dried specimens only) of Dr. Gray 

 and Mr. Carter to be guided by together with the figures of the former. Those of 

 Dehitella bore a general resemblance to the specimen in question which was 

 placed provisionally in that genus as a new species. Through the courtesy of Dr. 

 E. P. Ramsay I have since been able to examine specimens of Ceratella and Dehitella 

 from the Australian Museum, Sydney, and have received from there specimens 

 obtained from the New South Wales coast, and from Lord Howe Islands by Mr. 

 Whitelegge, to whom I am much indebted for kind assistance and information. The 

 examination of these specimens has shown that the form with which this paper deals 

 differs in such important points not only from the Hydractiniida3 but also from 

 the Ceratelladae that it must be placed in a separate family and I desire to here record 

 my indebtedness to the authorities of the Australian Museum, Sydney, for tlie 

 courteous assistance received from them. 



* Proc. Zool. Soc, Nov., 1868. 



