46 THE VOYAGE OF H.M.S. CHALLENGER. 
an inch in length, and though pinnate at their origin, are all directed unilaterally towards 
the distal ends of the main stems. Hydrothece deep, flask-shaped, with a deep antero— 
posterior constriction just below the margin ; margin entire, directed forwards ; mesial 
nematophore adnate to the hydrotheca wall for nearly half the height of the wall, and 
then continued for about the same distance as a free beak-like process, which is provided 
with a lateral as well as a terminal orifice ; lateral nematophores in the form of long 
tubular cylindrical processes, which project far beyond the margin of the hydrotheca, 
Gonosome not known. 
The type of form presented by the hydrotheca of the present species is very remark- 
able. The deep antero-posterior constriction, the nearly vertical direction of the hydrotheca 
mouth, with its even margin, so exceptional among the Statoplean Plumularidee, and the 
long cylindrical lateral nematophores which project like a pair of ears over the margin, 
confer on it an aspect singular and strikmg. The constriction below the hydrotheca 
mouth is entirely confined to the antero-posterior direction, so that though very striking 
in profile, it is not apparent in a front view of the hydrotheca. 
Fic, 3. Origin of a primary pinna in Lytocarpus longicornis, showing the splice-like joint 
near the proximal end of the pinna. 
a, Main stem. 
4, Proximal portion of pinna. 
ce, Distal portion. The bases of the secondary pinne or hydrocladia are seen with a secund disposition, along 
the length of the primary pinne. 
d, Splice-like joint separating the proximal from the distal portion of the primary pinna, and filled with 
a colourless chitin, 
The doubly pinnate ramification of the colony, with the unilateral direction of the very 
short hydrocladia, afford other striking characters. The hydrocladia are carried each on 
the summit of a strong process of the primary pinne, and being all directed towards one 
side of these, their really pinnate disposition may be easily overlooked. The basal 
process on which each stands has on its inner side a tubular nematophore. 
The primary pinnze, or those which being themselves destitute of hydrothece: support 
Ne 
