14 OPLORHIZA. 
rather long peduncles from a creeping filament, very delicate and filmy, 
deep, tapering toward the base, where they gradually pass into the peduncle 
without any definite line of demarcation. 
Gonosome not known. 
Dredged south of Tortugas from a depth of 260 fathoms. 
OPLORHIZA ALLMAN nov. gen. 
Greverto Cuaracter. Zrophosome.— Hydrothece tubular, provided with 
a floor and having the orifice cut into thin collapsible segments; borne by 
peduncles which spring from a creeping network of tubes. Hydrorhizal 
network carrying peculiar appendages which are in the form of tubular re- 
ceptacles with an orifice in the summit, and which enclose a granular, fleshy 
column, supporting a cluster of thread-cells. 
Gonosome not known. 
The genus Oplorhiza is nearly allied to Lafoéina Sars. In Lafoéina, 
however, the hydrotheex are absolutely sessile on the hydrorhiza, and their 
cavity passes directly into that of the hydrorhiza without the intervention 
of an infrathecal diaphragm or floor. 
The genus Lafoéina was established by Michael Sars for a little Lafoéa 
like hydroid (Lafoéina tenuis) obtained off the Norwegian coast, and essen- 
tially distinguished from Lafoéa by the presence of peculiar urticating 
appendages which are borne by the hydrorhiza* These appendages in 
Lafoéina are long, filiform, and flexuous, while in Oplorhiza they are short 
and cup-shaped. In both genera they remind us strongly of the nemato- 
phores of the Plumularidx. Like these they consist of a chitinous receptacle 
with fleshy contents which are probably of a simply sarcodic nature, and in 
which thread-cells are immersed. In the species on which the genus Oplo-~ 
rhiza is founded, these contents extend through the proximal part of the 
appendage in the form of a cylindrical column, which towards the summit 
becomes enlarged into a bulb in which numerous very long, curved thread- 
cells are imbedded. A very similar condition exists in Lafoéina tenuis. 
of the hydrothece. A more important character, however, will be found in the absence of any defi- 
nite floor or basal diaphragm in the hydrothece. It is the only known operculate form of the Cam- 
panuline in which the cavity of the hydrotheca thus passes uninterruptedly into that of the supporting 
tube as in the non-operculate genus Lafoéa. The sessile or pedunculate condition must be regarded 
as of merely secondary or specific value. 
* G. O. Sars, Bidrag til Kundskaben om Norges Hydroider, Forhandlinger i Videnskabs-selskabet i 
Christiania, 1873, p. 119. 
