HY DROIDS OF THE WOODS HOLE REGION. 
351 
Obelia geniculata (Linn. ) =Eucope diaphana L. Ag. (in part) =Eucope alternata A. Ag. Fig. 38. 
( Sertularia geniculata Linn., Syst. Nat., p. 1312.) 
Trophosome. — Colony usually consisting of a single geniculate stem bearing alternate pedicels on 
broad shoulder-like processes. Pedicels short, usually with 4 to 6 annulations. Hydrothecse short, 
campanulate or subtriangular. 
Gonosome. — -Gonangia long, tapering gradually to basal end and terminating in a collar which is 
beveled and convex on its surface. Medusae at liberation disk-shaped, with 24 marginal tentacles. 
Distribution. — Growing profusely on docks, floating seaweed, etc. One of the commonest species 
in the Woods Hole region. 
Obelia gelatinosa (Pallas) = Laomedea gigantea A. Ag. (teste Verrill). Fig. 39. 
( Sertularia gelatinosa Pallas, Elenchus Zoophytorum, p. 116.) 
Trophosome. — Colony sometimes attaining a height of 15 to 20 inches, profusely branched in a 
dendritic manner. Stem fascicled, with geniculate branches. Pedicels usually quite short, with 3 to 
5 annulations. Hydrothecse small, campanulate or 
subtriangular; margins armed with castellated or 
bimucronate teeth. 
Gonosome. — -Gonangia rather small, ovate, with 
collared aperture. Medusas with 16 tentacles at time 
of liberation (Hincks). 
Distribution. — Shallow water, often between tides, 
attached to timbers, etc. New Haven. Rhode Island 
coast. Vineyard Sound. 
Obelia bicuspidata Clark. Fig. 40. 
(Trans. Conn. Acad, of Sci., m, p. 58.) 
Trophosome. — Colony attaining a height of 
about 33 inches. Stem fascicled, straight, irregu- 
larly branched. Pedicels longer than in the next 
species, and with 10 to 15 annulations. Hydrothecse 
very deep, tubular, their margins armed with bimu- 
cronate teeth, between which lines originate which 
pass down the surface of the hydrothecse. 
Gonosome. — Unknown. 
Distribution. — Found at a depth of 3 to 5 fathoms, from reefs near Thimble Island. Near Woods 
Hole, 19 fathoms. 
Obelia longissima (Pallas). Fig. 41. 
(Sertularia longissima Pallas, Elenchus Zoophytorum, p. 119.) 
Trophosome. — Colony attaining a height of 12 to 14 inches. Main stem fascicled, flexuose, giving 
off branches, which themselves branch in a palmate manner, the whole thus being subvertieillate in 
effect. Pedicels of varying length, usually extensively annulated. Hydrothecse rather deep, cam- 
panulate, the margins appearing at first sight to be without teeth, but upon careful examination 
proving to be armed with very shallow, regularly undulating teeth. 
Gonosome. — Gonangia ovate, with collared apertures. Medusa- at the time of liberation with 20 
to 24 tentacles (Hincks). 
Distribution. — Woods Hole. Off Gay Head. Dredged by the Fish Hawk at station 7051, about 40 
miles southeast of No Mans Land; depth, 3 fathoms. 
As described by Hincks, this species has not a fascicled stem. Authentic specimens from England, 
however, have distinctly fascicled stems and agree well with American specimens. 
Obelia bidentata Clark. 
(Trans. Conn. Acad, of Sci., in, p. 58.) 
Trophosome. — Like that of 0. bicuspidata, except that it attains a larger size, has shorter pedicels, 
with 4 to 6 annulations, and proportionately wider hydrothecse. 
Clark. 
A. Outline of aperture of 
liydrothcca. 
