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DEPAttTME^'T OF THE NAVAL SERVICE 



Ohelia geniculata (Linnaeus). 



Trohphosome. Stem simple, geniculate, 25 mm. 

 high, hearing alternate pedicels on shoulder processes 

 of the internodes; hydrotheca as wide as deep; margin 

 entire; pedicels annulated at each end or throughout, 

 usually curved away from the stem. 



Gonosome. Gonangium axillary, oval or slightly 

 obovate; terminal collar present. 



Ohelia hyalina Clark. 



TropJiosome. Stem 20mm. high, unbranched or 

 occasionally branched, geniculate, with several annu- 

 lations above the origin of each pedicel; hydrotheca 

 as wide as deep; margin entire, sometimes flaring; 

 pedicels annulated at each end or throughout. 



Gonosonve. Gonangium axillary, obovate, with or 

 without terminal collar. 



Ohelia longissima (Pallas). 



Trophosome. Stem filiform of great length, 60 cm., 

 much branched, branches alternate; stem horn colour or 

 black, annulated at base and above each node; hydro- 

 theca deeper than wide; margin wavy or with low, 

 rounded teeth; pedicel annulated at each end or 

 throughout. 



Gonosome. Gonangium axillary, oval, with a dis- 

 tinct collar, pedicel annulated. 



No. 49. 

 Obelia geniculata. 



No. 50. 

 Obelia hyalina. 



No. 51. 

 Obelia longissima. 



Family CAMPANULINID^. 



Tropliosoyne. Colonies branched or unbranched; hydrothecae pedicellate or ses- 

 sile, always operculate, the operculum formed of converging segments; hydranths 

 with conical proboscis. 



Gonosome. Gonophores producing fixed sporosacs or free medusse. 



KEY TO GENERA. 



a Hydrotheca pedicellate. 



h Hydrotheca] margin distinct. 



c Operculum of several converging segments. Calycella. 



cc Operculum of four segments. Tetrapoma. 



ccc Operculiim shaped like an A-tent. Stegopoma. 

 hh Hydrothecal margin not distinct. 



Reproduction by fixed sporosacs. Opercular ella. 

 aa Hydrotheca sessile. 



Hydrotheca tubular, margin indistinct. Cuspidella. 



Trophosome. A creeping stolon gives rise to tubular hydrothecae on annulated 

 pedicels; margin distinct; several segments to the operculum. 



Gonosome. Gonangia borne on the stolon; acrocysts produced. 



