38 C. McLEAN FRASEE 



Genus OBELIA 



TropJiosome. — Stem branched, simple or fascicled; liydro- 

 thecae with thin walls. 



Gonosome. — Keproduction by means of free medusae, that when 

 liberated, possess more than eight marginal tentacles but no 

 mouth tentacles. Eight interradial lithocysts are present. 



OBELIA BOREALIS Nutting 

 Obelia borealis Nutting, Hydroids of the Harriman Ex. 1901, p. 174. 

 Distribution. — Yakutat, Alaska (Nutting) ; Ucluelet, San Juan 

 Archipelago. 



OBELIA COMMISSUBALIS McCready 



Obelia commissuralis McCready, Gymno. Charleston Har., 1858, p. 95. 

 Obelia commissuralis Torrey, Hydroida of the Pacific Coast, 1902, p. 56. 



Distribution. — San Francisco Bay (Torrey). 



OBELIA CORONA Torrey 

 Obelia corona Torrey, Hydroids of San Diego, 1904, p. 14. 

 Distribution. — San Diego (Torrey) ; San Juan Archipelago. 



OBELIA DICHOTOMA (Linnanis) 



Sertularia dichotoma Linn^us, Systema Natura^, 1756, p. 812. 

 Obelia dichotoma Calkins, Some Hydroids of Puget Sound, 1899, p. 741. 

 Obelia dichotoma Nutting, Hydroids of the Harriman Ex. 1901, p. 173. 

 Obelia dichotoma Torrey, Hydroida of the Pacific Coast, 1902, p. 57. 

 Obelia dichotoma Torrey, Hydroids of San Diego, 1904. p. 15. 



Distribution. — Bremerton (Calkins) ; Sitka, Berg Inlet, Orca, 

 Alaska (Nutting) ; San Pedro to Coronado Islands, San Diego, 

 Cal. (Torrey) ; Departure Bay, San Juan Archipelago. 



OBELIA DUBIA Nutting 



PI. Ill, Figs. 3-4 



Obelia diibia Nutting, Hydroids of the Harriman Ex. 1901, p. 174. 



Distribution. — Orca, Alaska (Nutting) ; Departure Bay, 

 Dodd's Narrows, Ucluelet, San Juan Archipelago. 



The gonosome of this si^ecies has not, hitherto, been described. 

 In the majority of specimens examined there Avere no gonosomes 

 present, but where they were present, there was one in the axil 

 of each of the lower pedicels or branches. The pedicels which 

 supported them are annulated throughout, varying in length but 

 never very long. The gonangium is pear-shaj^ed and is provided 



