380 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
colonies. I know of no means of distinguishing this species from the preceding except that the ten- 
tacles may be 20 instead of 24. 
Distribution . — The hydroid colonies have been found at Woods Hole and off Gay Head. 
Obelia flabellata (Ilincks) l =Eucope polygena A. Ag.? 2 
( l Ann. and Mag. Nat. Hist., 3d series, vol. xvm, p. ‘297. 2 North Amer- 
ican Acalephse, p. 8G.) 
Differs from the preceding in no constant feature that 
1 am aware of. 
Distribution . — Woods Hole; off Thimble Island (Ver- 
nll ) . 
Obelia commissuralis McCr. Fig. 97. 
(Proc. Elliott Soc., vol. i, No. 1, p. 197.) 
Bell disk-shaped. Marginal tentacles 16 at time of 
liberation, long and slender. Ovaries not developed at 
time of liberation. 
Distribution . — Colonies abundant in Woods Hole 
region, growing on piling of wharves and on submerged 
timbers generally. 
97. Obelia commissuralis McCr. 
98. Obelia gcniculata (Linn.) 
Obelia geniculata (Linn.). Figs. 39A, 98. 
{Sertularia geniculata Linn., Syst. Nat., p. 1312.) 
Bell disk-shaped, or shallow bowl-shaped. Marginal tenta- 
cles 24 at birth, each with an inward projecting spur. Otocysts 8, 
two between each two radial canals, placed over the bases of the 
tentacles and not between them. Proboscis short, with four 
inconspicuous lobular lips. Radial canals 4. Ovaries oval, hang- 
ing beneath the middle portion of the radial canals. No sense- 
bulbs. This, like other species of Obelia, has the habit of swimming with the bell reversed, so that it 
appears somewhat like an umbrella turned wrong side out. 
Colors . — The only color is in the light-yellowish ovaries and proboscis. 
Distribution . — Abundant throughout Woods Hole region. 
Obelia gelatinosa (Pallas ) 1 =mmimdea. gigantea A. Ag. 2 (Verrill). 
( x Sertularia gelatinosa Pallas, Elenchus Zoophytoram, p. 116. 2 North American Acalephie, p. 94.) 
Bell disk-shaped. Tentacles 16 at time of liberation, each with an inward-projecting spur. 
Otocysts 8, placed over bases of tentacles. Proboscis short, with mouth surrounded by four lobular 
lips or mouth-arms. Radial canals 4. Ovaries round, hanging beneath middle part of radial canals. 
Colors . — Ovaries and proboscis light-yellowish. 
Distribution . — Colonies have been found growing at New Haven, Conn. ; along the Rhode Island 
coast, and in Vineyard Sound. 
Obelia dichotoma (Linn.). 
( Sertularia dichotoma Linn., Syst. Nat., p. 1312.) 
Bell very shallow, disk -shaped. Marginal tentacles 16 at time of 
liberation. Not distinguishable from the preceding. 
Distribution . — Colonies dredged off Gay Head, 1 fathom (Verrill). 
Oceania singularis Mayer. Fig. 99. 
(Bull. Mus. Comp. Zool., vol. xxxviii, No. 1, p. 7.) 
Bell rather shallow, flaring decidedly at margin, and with a well 
marked dome-shaped apical projection. Marginal tentacles 16, each bearing a sense-bulb at its base. 
There are rudimentary tentacles between bases of larger ones. Proboscis not extending beyond 
velum, and ending in four broad lobes or mouth-arms that are not fimbriated. Radial canals 4, bearing 
the ovaries on their upper portion. There is an otocyst between each pair of tentacles, including the 
rudimentary ones. 
99. Oceania singularis Mayer. 
