A FURTHER NOTE ON KERATOSUM COMPLEXUM. 



CHARLES W. HARGITT. 



In my original description of this anomalous hydroid, 1 it was 

 stated that not only was it necessary to create for it a new genus 

 as well as species, but that there "might be the necessity of 

 establishing for it a new family." It was further said: "Con- 

 cerning the family relations I am not disposed in this connection 

 to enter into any critical review. While the Perisiphonidae would 

 be the only one under which it might be placed, still this family 

 as at present denned . . . would by no means provide for the 

 species. For example, while there is an axial tubular mass, as 

 show r n in Fig. 9, there is no single one of these which bears the 

 hydrothecae as called for by the definition referred to. However, 

 the species may be left under this family till such time as adequate 

 revision may be undertaken, when needed modifications may 

 be provided." 



I have since found access to a paper by W. Baldwin Spencer, 

 entitled "A New Family of Hydroidea, Together with a Descrip- 

 tion of the Structure of a New Species of Plumularia," pub- 

 lished in The Transactions of the Royal Society of Victoria, 1890, 

 a publication of very limited circulation. Had this account 

 been available to me at the time of my perplexity concerning 

 the family relations of Keratosum it would have greatly facili- 

 tated my insight into many features which were extremely 

 puzzling. I take the first opportunity to acid to my earlier 

 account what seems to be a solution of the point left in abey- 

 ance pending further knowledge. 



Spencer established the family Hydroceratinidae for a rather 

 remarkable hydroid obtained from Port Phillip having much in 

 common with Keratosum in both structure and habit, though 

 with very sharp differences, the details of which need not be 

 given here since only the matter of its family features are in 

 question. One interesting point of coincidence may be cited, 

 namely, that Baldwin at first referred his specimen to the family 



1 BIOL. BULL., Vol. XVII., p. 379. 



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