THE HYDROIDS 



than the hydrothecae and sometimes considerably shorter, without a 

 definite swelling below the hydrothecae. Hydrothecae immense, in 

 one case nearly -^ of an inch in height, long, tubular-urceolate, ex- 

 panded distally, with slightly everted and broadly sinuous margin. 

 The margin is reduplicated in one specimen. Hydranth with about 

 twenty tentacles. 



Gonosome. Not known. 



Distribution. Orca, Prince William Sound, Alaska (W. R. Coe, 

 Harriman Exped.). 



This species is closely allied to C. grandis Allman, 1 and may be 

 identical with it although it differs from Allman's description in the 

 character of the pedicels which he describes as having distinct node- 

 like enlargements immediately below the hydrothecse. The hydro- 

 thecse are larger than those of any other campanularian known to me. 

 But one small colony was found and it was creeping over another 

 hydroid. 



OBELIA. 



Trophosome. Colony regularly branching ; stem simple or com- 

 pound. Hydrothecss campanulate, thin, never with greatly thickened 

 walls. 



Gonosome. Reproduction by means of medusae which are disk- 

 shaped, with four radial canals, more than eight marginal tentacles, 

 eight interradial lithocysts and a short manubrium without mouth ten- 

 tacles. 



OBELIA DICHOTOMA (Linn.). 



Sertitlaria dichotoma LINN., Systema Naturae, Ed. x, p. 812. 1758. 



Obelia dichotoma SCHULZE, Nordsee Expedition, Hydroida, p. 129, 1872. 

 VERRILL, Preliminary check-list Marine Invertebrates of Atlantic coast, 

 p. 1 6, 1879. CALKINS, Some Hydroids from Puget Sound, Proc. Boston 

 Soc. Nat. Hist., Vol. xxvin, No. 13, p. 256, 1899. 



Distribution. Sitka, Berg Inlet, and Orca, Alaska (Harriman 

 Exped.) ; British Coast (Hincks) ; Helgoland (Schulze) ; Puget 

 Sound (Calkins). 



OBELIA PLICATA Hincks. 



Obelia plicata HINCKS, British Hydroid Zoophytes, p. 159, 1868. NUTTING, 

 Hydroida from Alaska and Puget Sound, Proc. U. S. Nat. Mus., Vol. 

 xxi, No. 13, p. 741, 1899. 



Distribution. Orca, Alaska (Harriman Exped.) ; Puget Sound 

 (Nutting) ; British Coasts (Hincks). 



1 Diagnoses of new Genera and Species of Hydroida ; Linnaean Soc. Jour. 

 Zoology, Vol. xi, p. 259. 



