with Observations on Australian Hydroids. 89 



latter supposition be correct, there is nothing to separate the 

 genus from Ly tocarpus, one species of which (L. racemiferus) 

 has the nematocladia all together in one portion of the 

 branch. The form of the tubular sarcothecse on the ribs, how- 

 ever, approximates most nearly to that found in some species 

 of Cladocarpus^ and the fact that they are described as pro- 

 jecting at right angles on all sides of the ribs does not favour 

 the theory that the latter are modified pinnae, as when this is 

 the case the sarcothecas are arranged symmetrically in the 

 same median or lateral positions which they would occupy if 

 the hydrothec^ were present. A remarkable feature of 

 P. ramosa is the presence on the most proximal part of the 

 fertile branch, where no pinnae are produced, of a series of 

 hydrothec^. Professor Allman suggests that they may be 

 nematophores, which have been mistaken for hydrothecas, 

 and there is no doubt that the structure strikingly resembles 

 in appearance the proximal part of the ordinary branches 

 in such species as Aglaophenia divaiicata, which are 

 destitute of pinnae, and bear a central series of large sar- 

 cothecae. I know of no case among the Statoplea where 

 hydro thecae are regularly borne directly on a stem or branch, 

 though I have met with an abnormal instance of such a 

 case. 



AcANTHOCLADiUM, Allman. 



Hydrocladia replaced by spines at the tips of the branches; 

 remainder of trophosome and gonosome as in Aglaophenia. 



This genus is distinguished, like Acanthella among the 

 Eleutheroplea, by having the pinnse at and near tlie tips of 

 the branches in the form of hollow spines, destitute of 

 hydro thecae. The ribs of the corbula in A. Huxleyi are not 

 flattened, and each bears a hydrotheca. 



Pentandra, Yon Lendenfeld. 



Hydrocladia pinnately arranged, a mesial and two pairs 

 •of lateral sarcothecae adnate to each hydrotheca. 



Gonosome a corbula, as in Aglaophenia. 



Two species of this very distinct genus have been described 

 by Dr. von Lendenfeld. The hydrothecge resemble those of 

 a typical Aglaophenia, with tubular mesial and lateral sar- 

 cothecae in the usual positions, but possess, in addition, a 

 second pair of laterals, which are adnate to the sides of the 

 hydrotheca as far as the margin, above which, in both species, 



