46 



THE VOYAGE OF H.M.R. CHALLENGER. 



an inch in length, and though pinnate at their origin, are all directed unilaterally towards 

 the distal ends of the main stems. Hydrothecas deep, flask-shaped, with a deep antero- 

 posterior constriction just below the margin ; margin entire, dii'ected forwards ; mesial 

 nematophore adnate to the hydi'otheca 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 hydrothecn. 



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 h3'drotheca 

 mouth, with its even margin, so exceptional among the Statoplean Plumularidai, and the 

 long cylindrical lateral nematophores which project like a pair- of ears over the margin, 

 confer on it an aspect singular and striking. 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. 



Fio. 3. Origin of a inimary pinna in Lytocnrpns lonqiconiix, showing the splicelilie joint 

 near tlie ]iroximal euil of tlie pinna, 

 o. Main stem. 

 4. Proximal portion of pinna. 



c. Distal portion. The bases of the secomlnry pinna? or hydrooladia are seen with a seeun'l disposition, along 



the length of the primary i)inna>. 



d. Splice-like joint sep.arating tlie 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 verj- 

 short hydrocladia, aff"ord other striking characters. The hydrocladia are carried each on 

 the summit of a strong proce.ss of the primary pinna?, 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 pinnae, or those which being themselves destitute of hydrothecse support 



