108 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.4 



and that just at the entrance, off Point Piastla. This might be taken 

 to indicate that there is nothing in common in the waters to the west- 

 ward of Lower Cah'fornia and those in the Gulf of California, were 

 it not for the fact that of the 38 previously described species obtained 

 in the Gulf of California in this collection twelve were obtained from 

 the west coast in the 1934 collection. The 1934 collection was all from 

 Cerros Island south; the 1936 and 1937 collections, north of Cerros 

 Island. 



The hydroid fauna of the Gulf seems to be rather a mixture. While 

 that of the west coast of Lower California is definitely northeast Pacific 

 in type, that of the Gulf, if this collection is representative, is a mixture 

 of species from the north and from the south, the latter related to those 

 from the West Indian region. 



Of the 38 species above referred to, 22 have been reported from 

 the Pacific, north of the Mexican boundary, and 25 from the Atlantic, 

 but as 15 species have been reported in both of these areas, there are 

 left but seven North Pacific and ten Atlantic species that help to show 

 any trend. More extensive and intensive collecting must be done before 

 any definite conclusions can be drawn. 



The most striking feature of the hydroid fauna of the Gulf is the 

 preponderance of the Plumularidae, especially of Aglaophenia and 

 Antennularia. It is in these two genera that the most of the new species 

 were found. It may be that here there is a very suitable environment for 

 this family, or, on the other hand, it may be that as these, in general, 

 appear in robust colonies, they are more readily observed in general 

 collecting, in which case a more detailed examination of the fresh 

 material might produce a similar abundance in other families. That the 

 latter explanation is the probable one is indicated by the fact that there 

 were only four gymnoblastic species (there were 46 in the 1934 collec- 

 tion) and very few of the smaller campanularians. 



Synonymy 



Apart from those that are new, all of the species with the exception 

 of Plumularia attenuata Allman (Allman, G. J. Mem. Mus. Comp. 

 Zool. Harvard, 1877, p. 30) are mentioned and synonymy given either 

 in Hydroids of the 1934 Allan Hancock Pacific Expedition or in 

 Hydroids of the Pacific Coast of Canada and the United States (Fraser, 

 The University of Toronto Press, Toronto, 1937). It seems unneces- 

 sary to repeat the synonymy here. 



