362 



BULLETIN OF THE BUREAU OF FISHERIES. 



Fig. 21. — Obeha bicuspidata Clarke. A. 

 small colony; B. colony showing gono- 

 some. 



Distribution. — On Pennaria, Eudendrium and gorgonian stems, common; on piles of the United 

 States Bureau of Fisheries wharf, on the piles of the railroad bridge, Bogue Sound lo feet. North River 



8 to lofeet. 



In the colonies found on the Pennaria stems it is possible to 

 find enough variation to cover all the points given as differences 

 between O. bicuspidata and O. bidentaia, in Clarke's descriptions, so 

 that it is hardly possible that there are the two distinct species. 

 The gonosome has not been described hitherto 



Obelia dichotoma (Linnseus). 



Serlularia dichotoma Linnscus. Systema Naturae, 1767. p. 131J. 

 Obelia dichotoma Hargitt. American Naturalist, 1901, p.382. Nutting, Hy- 

 droids of Woods Hole, 1901, p. 350. 



Trophosome. — Colony branching, usually in a dichotomous 

 manner, though in the branches this may be quite irregular; two 

 or three annulations on the main stem and branches above each 

 branch and pedicel ; pedicels short, annulated throughout or at each 

 end only; hj'drothecae much deeper than wide, with straight sides; 

 margin entire, though in some cases it appears slightly wavy or 

 crenulated. 



Gonosome. — Gonophores usually borne in the axils of the 

 pedicels, obovate with a distinct collar which narrows from base 

 to tip, somewhat rounded at the end, making a collar quite 

 characteristic; pedicels distinct, with 3 to 6 annulations. 



Distribution. — On barnacles found growing on the sea buoy. 



The hydrotheCEe are smaller in these specimens than in those found farther north. 



Obelia geniculata (Linnseus). 



Sertularia geniculata Liimaeus, Systema 

 Naturae, 1767, p. 1312. 



Obelia geniculata Hargitt, American Na- 

 turalist, 1901. p. 382. Nutting, Hy- 

 droids of Woods Hole. 1901, p. 351. 



Trophosome. — Colony usually con- 

 sisting of a single geniculate stem, an 

 inch or less high, bearing alternate 

 pedicelson shoulder processes; pedicels 

 short, curved so that their hydro- 

 thecae often lie W'ith their long axes 

 horizontal; annulated throughout or 

 with the central portion smooth; hydro-. 

 thecse broadly campanulate, depth 

 and width being nearly equal; margin 

 entire. 



Gonosome. — Gonophores borne in 

 the axils of the pedicels; gonangia 

 nearly oval but tapering slightly to 

 the base, distally provided with a distinct collar that is the same size throughout, 



Distribution. — On the crab float at the United States Bureau of Fisheries wharf. 



Obelia dichotoma (Linnaeus). A, part of colony to show mode of 

 branching; B, gonosome. 



