HXDROIDS FROM NOVA SCOTIA 
167 
Genus Obelia. 
Obelia commissuralis McCrady. 
Obelia commissuralis McCrady, Gymno. Charleston har., 
1858, p. 95. 
Obelia commissuralis Nutting, Hydroids of Woods Hole, 1901, 
p. 350. 
Obelia commissuralis Whiteaves, Marine Invert. Eastern Can., 
1901, p. 23. 
The commonest campanularian of the region; on rocks, piles, 
seaweeds, etc., at or below low water, Canso. 
Obelia dichotoma (Linnaeus). 
Sertularia dichotoma Linnaeus, Systems Naturae, 1758, p. 812. 
Obelia dichotoma Nutting, Hydroids of Woods Hole, 1901, p. 
350. 
Obelia dichotoma Whiteaves, Marine Invert. Eastern Can., 
1901, p. 23. 
Common on Laminaria, at and below water, Canso. 
Obelia geniculata (Linnaeus). 
Plate XII, figs. 1 and 2. 
Sertularia geniculata Linnaeus, Systema Naturae, 1767, p. 1312. 
Obelia geniculata Nutting, Hydroids of Woods Hole, 1901, p. 
350. 
Obelia geniculata Whiteaves, Marine Invert. Eastern Can., 
1901, p. 23. 
In 3 fathoms, Barrington Passage; on laminaria and other 
seaweeds, on piles, etc., at low water, Canso. 
Some abnormal specimens of this species were found growing 
on Lemargus margilis — a copepod, parasitic on a sunfish ( Mola 
mola), caught in Ghedabucto bay. In normal specimens, the 
hydrothecse appear in regular alternation to give the regular 
geniculate appearance of the stem. The gonophores appear in 
the axils, being regularly disposed but not in any way affecting 
the geniculation of the stem. In this case the gonophores take 
the place of the hydrothecse., making up a portion of the regular 
geniculate arrangement, and do not appear in the axils. 
24853—11 
