NO. 5 fraser: hydroids 213 



Obelia biserialis, new species 

 Plate 24, Fig. 6 



Trophosome. — Colony with a well marked, fascicled, main stem, with 

 branches biserially arranged in the same plane, much like those in many 

 of the species in the Sertularidae but unusual in the Campanularidae. 

 These branches are given off in regular alternation ; they are not fascicled 

 and not branched again, Hydrothecae appear in the axils of the branches, 

 and, arranged alternately, throughout the whole length of each branch. 

 The hydrotheca increases in diameter gradually from base to margin, but 

 the sides are straight and there is no flare at the margin. It is much the 

 same size and shape as in O. plicata Hincks, but in this species some flar- 

 ing takes place; the margin is entire and circular. In all of the hydro- 

 thecae except the terminal one on each branch, the pedicel is short, about 

 the same length as the hydrotheca, and is annulated throughout, the annu- 

 lations tending to be oblique. The longer pedicel of the terminal hj^dro- 

 theca is annulated at both ends only. 



Gonosome. — The gonangia are small, appearing in the axils of the 

 more distant hydrothecae, little longer than the hydrothecae, and slender, 

 less than 0.2 mm in greatest width. The distal end is rounded with the 

 small aperture at the center. 



Distribution. — Station 919-39, off Sulphur Bay, Clarion Island, 25- 

 26 fathoms; north of Clarion Island, 25-26 fathoms; off Braithwaite 

 Bay, Socorro Island, 17-46 fathoms. 



Obelia castellata Clarke 

 Obelia castellata Clarke, Bull. Mus. Comp. Zool.,Harvard, 1894, p. 73. 

 Distribution. — San Francisco Bay, east of Panama City, Panama, 

 shore. 



Obelia commissuralis McCrady 

 Obelia commissuralis McCrady, Gymno. Charleston Har., 1859, p. 197. 



Fraser, Hyd. Pacific Coast, 1937, p. 84. 

 Fraser, Hancock Hyd., 1, 1938, p. 36. 

 Fraser, ibid., 3, 1938, p. 133. 



Distribution. — East of Point Fermin, Calif., shore; 5 miles— 152° 

 from San Pedro breakwater, 17-19 fathoms; 1 mile east of Empire Land- 

 ing, Santa Catalina Island, 18 fathoms; 3 miles west of Natividad Island, 

 Lower Calif,, 30-31 fathoms. 



