DESCRIPTION OF GENERA AND SPECIES. 
PLUMULARID. 
KELEUTHEROPLEA., 
Sub-family 
Plumularia, Lamk. (in part). 
Plumularia, Lamarck, Hist. Nat. des An. sans Vert., Ist ed., 1815, 
Aglaophenia, Lamouroux, Hist. des Pol. Coral. flex., 1816. 
Plumularia flabellum, n. sp. (Pl. 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, hydrocladia alternate, averaging about 
three-tenths of an inch in length; hydrotheca-bearing internodes separated from one 
another by a single internode destitute of hydrotheea. Hydrotheca adnate by its entire 
height to its internode; hydrotheeal 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 flabellum is a very beautiful Hydroid. Its primary branches, which are 
of unequal length, and given off 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 hydrothece, 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 off Marion Island, 26th December 1873, from a depth 
of 50-75 fathoms. 
Plumularia lawa, n. sp. (PI. I. figs. 5, 6). 
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 
