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. 



Generic Character. Trophosome. — Hydrotheca3 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 Lafoeina Sars. In Lafoeina, 

 however, the hydrothecae 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 Lafoeina was established by Michael Sars for a little Lafoea 

 like hydroid [Lafotina tenuis) obtained off the Norwegian coast, and essen- 

 tially distinguished from Lafoea by the presence of peculiar urticating 

 appendages which are borne by the hydrorhiza.* These appendages in 

 Lafoeina 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 Plumularidse. 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 Lafoeina tenuis. 



of the hydrothecK. A more important character, however, will be found in the absence of any defi- 

 nite floor or basal diaphragm in the hydrothecse. It is the only known operculate form of the Cam- 

 panulinffi in which the cavity of the hydrotheca thus passes uninterruptedly into that of the supporting 

 tube as in the non-operculate genus Lafoea. 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 



ChrMania, 1873, p. H9. 



