OBELIA MARGINATA. 9 



short, alternate liydranth-bearing ramuli which are marked at their origin 

 by spiral corrugations, and which, increasing in thickness towards their distal 

 ends, gradually pass into the piriform body of the hydranth; perisarc very 

 opaque. Hydranths large, assuming for the most part a drooping attitude. 

 Gonosome. — Gonophores (male ?) oviform, supported on short spirally 

 corrugated peduncles, scattered on the hydrocaulus. 



Dredged at Tortugas in shallow water. 



The massive-looking hydranths and the enlargement of the hydrocaulus 

 towards their base give a peculiar aspect to this little hydroid. The peri- 

 sarc, which is very opaque, is apparently continued for some distance over 

 the tentacles, as in li. vestita Wright, the only species of the genus hitherto 

 described. In the condition of the specimens of B. hiimilis, however, it was 

 not possible to make this out satisfactorily. 



The massive hydranths and comparatively slight development of the 

 hydrocaulus distinguish this species from B. vestita. In both species the 

 hydranths exhibit a tendency to assume a drooping attitude. 



It occurred in considerable profusion, creeping over the surface of a sea- 

 weed which it covered with a low but rather dense growth. 



Suborder CALYPTOBLASTEA. 



Tribe CAMPANULIN.S:. 



Family CAMPANULARID^. 



Genus OBELIA Peron & Lesueur. 



Obelia marginata. 

 PI. VI. Figs. 1, 2. 



Trophosome. — Stem attaining a height of nine inches, monosiphonic, pin- 

 nately branched ; pinnae alternate ; stem and pinnte gently zigzag, with a 

 strong short process given off from the salient angle of each geniculation, 

 and with a joint at the distal side of the process. Hydrothecaj supported 

 on short stout peduncles which rest on the processes of the stem and 

 pinnae, large, nearly cylindrical, slightly oblique at the inner side of the 

 base, and with a circular even orifice which is margined by a narrow, more 

 transparent rim. 



Gonosome not known. 



Dredged off Logger-Head Key from a depth of 9 fathoms. 

 2 



