DESCRIPTION OF GENERA AND SPECIES. 



PLUMULARIDyE. 



Sub-family — E leutheroplea. 

 Plumularia, Lamk. (in part). 



Plumularia, Lamarck, Hist. Nat. des An. sans Vert., 1st ed., 1815. 

 Aglaophenia, Lamouroux, Hist, des Pol. Coral, flex., 1816. 



Phmiularia fiabellwn, n. sp. (PI. I. figs. 1-4). 



Trophosome. — Colony attaining a height of about five inches, stem springing from a 

 dense mass of entangled filaments, much branched, branches pinnately disposed, main 

 stem and principal branches strongly fascicled, hydi'ocladia alternate, averaging about 

 three-tenths of an inch in length ; hydrotheca-bearing internodes separated from one 

 another by a single internode destitute of hydrotheca. Hydi-otheca adnate by its entire 

 height to its internode ; hydrothecal internode carrying, besides the pair of lateral 

 nematophores, a single mesial nematophore, which springs from a point at some distance 

 below the hydrotheca ; intervening internodes carrying a single mesial nematophore. 



Gonosome not known. 



Plumularia fiahellum is a very beautiful Hydroid. Its primary branches, which are 

 of unequal length, and given ofi" at irregular distances, are pinnately disposed and set 

 with hydrocladia, while many of the primary branches also send off pinnately-disposed 

 ramuli, which, like the primary branches, are themselves destitute of hydrothecse, but 

 carry pinnately-disposed hydrocladia. Hydrocladia are also borne by the main stem in 

 the intervals of the branches. The pinnate disposition of all the branches and ramuli, 

 and the fact of their lying in one and the same plane, confer upon the colony the flabelli- 

 form habit which has suggested the specific name. 



This fine species was dredged ofi" Marion Island, 26th December 1873, from a depth 

 of 50-75 fathoms. 



Plumularia laxa, n. sp. (PL I. figs. 5, G). 



Trophosome. — Colony attaining a height of about four inches, stem much and irregu- 

 larly branched, rooted by a dense mass of entangled filaments, main stem and principal 



