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DEPARTMENT OF THE NAVAL SERVICE 



Opercularella lacerata (Jolinston). 



Trophosome. Stem short, 25 mm., branched, some 

 of the branches being almost as long as the main stem; 

 stem and branches flexuous, annulated throughout; 

 hydrotheca with proximal half oval,' distal half conical ; 

 no distinct margin ; segments of the operculum long 

 and slender. 



Gonosome. Female gonangia obovate, sessile or on 

 short, annulated pedicels, axillary or in place of hydro- 

 thecae; male gonangia narrower. 



No. 55. \ 

 Opercularella lacerata. 



Opercularella pumila Clark. 



Trophosome. Stem erect or creeping, sparingly 

 branched, annulated throughout; hydrotheca3 similar in 

 shape to those of 0. lacerata but smaller. 



Gonosome. Gonangia fusiform on short annalated 

 pedicels on the stem or stolon. 



No. 56. 

 Oiicrculurclla piimila. 



Genus Stegopoma. 



Trophosome. Hydrotheca with an operculum formed of two membranes folded 

 lengthwise and which come together roof -like, with their long edges: each of these 

 is separated from the remainder of the hydrotheca by a curved line; at each side the 

 hydrothecal wall forms a triangular gable-like structure, between the two opercular 

 membranes. 



Gonosome. Gonophores producing fixed sporosacs. 



Stegopoma plicatile (Sars). 



Trophosome. Stem large; stem and main branches 

 fascicled; hydrotheca long, tubular or nearly so, sessile 

 or with a short pedicel. 



Gonosome. Gonangium long, oval or cylindrical, 

 adhering to the branch for a portion of the length. 



No. 57. 

 Stegopoma plicatile. 



Genus Tetrapoma. 



Trophosome. Hydrotheca? pedicellate, with distinct four-toothed margin, oper- 

 culum of four segments. 

 Gonosome. Unknown. 



