136 THE VOYAGE OF H.M.S. CHALLENGER. 



VerrilP added the genus Euplexaura for forms of which Eiiplexaura cctpensis may 

 be taken as a type, and in wliich the form of the spicules differs widely from those met 

 with iu the other genera ; the same author in his Notes on Radiata (Joe. cit.) describes the 

 family as having a "Corallum usually dichotomous and more or less arborescent. Axis 

 horn-like, or more or less calcareous, especially at base. Longitudinal ducts ecj^ual, 

 arranged regularly all round the axis. Coenenchyma usually thick. Cells scattered 

 over all parts of the surface, flat, or elevated on prominent verructe. Tentacles at base 

 and sides of the pol}-ps stifi'ened with large fusiform spicula. Spicula of the coenenchyma 

 usually large, of various forms, most frequently there are large warty spindles mino-led 

 with clubs or crosses." 



Verrill makes a new genus Psammogorgia, for Gorgonia fucosa, Val., &c., and 

 further, in his Critical Remarks on Polyps" he establishes another new genus Eunicella, 

 for Gorgonia vemicosa, P., and many allied forms. 



The genera belonging to the family as it now stands certainly require revision, but 

 to do this effectually it would be necessary to re-examine not only a very large number 

 of described species, but to investigate them in a well-preserved state, as there are not 

 wanting indications that differences exist in the minute structure of the axis and of the 

 polyps, in addition to the manifold differences in the form of the spicules ; the species 

 found during the voyage of the Challenger were but few in number, and it would be 

 premature to revise the group on the materials at our disposal. We therefore accept the 

 family as containing among others the following genera : — Eunicea, Lamk., Plexaiira, 

 Lamx., Psammogovgia, Verrill, Plexaurella, Roll., Eunicella, Verrill, and Euplexaura, 

 Verrill, this last genus being very nearly related to the Gorgonidte. Klunzinger would 

 refer the genus Plexaurella to the GorgoneUidse, on account of the structure of the axis, 

 but the axis in this latter family would appear to difi'er somewhat in the arrangement of 

 the longitudinal canals. 



Two new genera we have felt obliged to make for already known species, Plexauroides 

 and Pseudoplexaura, and, from an examination of numerous species in the Museums of 

 Paris and Turin, we think it very probable that still further divisions of the genera 

 Eunicea and Plexaura will have to be made. 



Species of the following genera have been found during the cruise of the Challenger: — 



Plexaura, Lamx. 

 Plexauroides, n. gen. 

 Plexaurella, Kolliker. 



Pseudoplexaura, n. gen. 

 Euplexaura, Verrill. 

 Eunicella, Verrill. 



> Proc. Essex Inst., vol. vi. p. 74, August 1869. ' Amer. Journ. Sci. and Arts, November 1869, p. 426. 



