256 MEDUS/E OF THE WORLD. 



This hydroid is abundant on the Atlantic coasts of Europe and in America north of the 

 Carolinas. It has been found by Saemundsson at Iceland, and by Hartlaub off the Pacific 

 coast of Chile and in the Straits of Magellan. Clarke records it from Alaska. 



Billard, 1904 (Annal. Sci. Nat., Ser. 8, Zool., tome 20), finds that at St. Vaast, on the 

 northwest coast of France, there are two varieties of O. longissima; a large form in deep water, 

 and a smaller variety along the shore; in which latter the indentations of the margin are greatly 

 reduced so as to be all but indistinguishable. 



This common Obeli a may be at once recognized by its long, flexible, black, thread-like, 

 main stems, and its delicate alternate branches, all tapering from base to summit. The mature 

 medusa can not be distinguished from that of other species of Obeha. 



Obelia chinensis Marktanner-Turneretscher. 

 Obelia chinensis, Marktanner-Turneretscher, 1890, Ann. Hofmuseum Wien, Bd. 5, p. 210, taf. 3, fign. 6, 7. 



Stems 100 mm. long, zigzag, sparingly branched, with 3 to 5 rings on each internode of the 

 main stem and at base of each branch. The pedicels of the hydrothecae are ringed at both 

 ends, but free of rings in the middle. Pedicels 0.5 to 0.9 mm. long. Hydrothecae bell-shaped, 

 with plain margin, 0.5 mm. long, and 0.3 to 0.4 mm. wide at the orifice. This form is closely 

 related to, if not identical with, 0. plana, but pedicels of hydrothecae are said to be longer. 



Yellow Sea, coast of China. 



Obelia nigra Browne. 



Obelia nigra, Browne, 1900, Proc. Royal Irish Acad., ser. 3, vol. 5, p. 721 ; 1903, Bergens Museums Aarbog, No. 4, p. 16; 1905, 

 Proc. Royal Soc. Edinburgh, vol. 25, p. 770. 



Mature medusa.— Bell slightly cone-shaped, 5.5 mm. wide, 150 to 200 tentacles. About 

 6 large black or brown basal bulbs in each quadrant; these are twice as large as the colorless 

 bulbs of the remaining tentacles. 8 lithocysts, each with one concretion. 4 radial-canals, 4 

 lips, 4 small globular gonads on outer halves of radial-canals two-thirds the distance from 

 stomach to margin of bell. English, Scottish, and Irish coasts; Bergen, Norway; Halifax 

 Harbor, Nova Scotia. Hydroid unknown. 



This Obelia medusa is readily distinguished by the dark-brown, almost black pigment at 

 the bases of some of the tentacles. I have taken it in considerable numbers in Halifax Harbor, 

 Nova Scotia, in September. Torrey, 1909 finds a medusa with purple tentacle-bulbs, on 

 the coast of California and has named it 0. purpurea. (See appendix.) 



Obelia (?) plicata Hincks. 



Obelia (?) plicata, Hincks, 1868, Hist. British Hydroid Zooph., p. 159, plate 30, fig. I. 

 Obelia plicata, Nutting, 1901, Proc. Washington Acad. Sci., vol. 3, p. 173. 



This is a coarse, tree-like hydroid about 15 to 20 mm. high. Main stem very thick at base, 

 but tapers upward to a thread-like end. It is composed of a bundle of delicate tubes closely 

 adherent one to the other. The branches are profuse and given off somewhat irregularly, 

 although more or less alternately. They are very long and taper as does the main stem. The 

 hydrothecas are conical, quite wide, and with even rims without notches or teeth. They are 

 mounted upon pedicels having about 4 to 12 rings. Reproductive calycles unknown. This 

 hydroid may not produce free medusa; and may possibly belong to the genus Campanula, to. 

 Hincks describes it from the Shetland Islands, and Nutting records it from Puget Sound and 

 Alaska. Medusa unknown. 



Obelia arruensis Marktanner-Turneretscher. 

 Obelia arruensis, Marktanner-Turneretscher, 1890, Annalen Hofmuseum Wien, p. 210, taf. 3, fig. 8. 



Stems about 50 mm. high. Branching similar to that of O. plicata Hincks, but with 

 somewhat longer pedicels of the hydrothecae. Hydrothecae bell-shaped, 0.6 mm. long, 0.36 

 mm. wide at the orifice, and with 14 to 18 teeth. Gonothecae arise in clusters from stem and 

 are about 0.7 mm. long, goblet-shaped, widest above. They resemble those of Campanuhna 

 turrita Hincks. Found at the Arru Islands, tropical Pacific. 



