NO. 4 FRASER : H YDROIDS 1 69 



When the Caribbean Sea was wide open to the Pacific, before the 

 Panama land connection appeared, the hydroid fauna of the West 

 Indian region must have been much similar to that of the contiguous 

 part of the Pacific since 85 species (out of 119, 71%) in this list have 

 been reported in the North Atlantic, mostly from the West Indian 

 region, or along the course of the Gulf Stream. These must all be old 

 established species. The Northeast Pacific, with all the ages since the 

 land connection was made, to the good, has much fewer species in com- 

 mon with the eastern tropical Pacific. 



As 40 species are common to the Northeast Pacific and to the North 

 Atlantic, there are still 45 species from the North Atlantic that have 

 not yet been reported from the Northeast Pacific. Table IV gives the 

 more detailed description of these 45 species. The proportions are much 

 as one should expect from an examination of the other tables. 



Table V shows detailed distribution of the hydroids obtained in the 

 vicinity of the Galapagos Islands. Of the 84 species obtained, 17, mostly 

 new, were not found in Division B or Division C, leaving 67 species 

 that were recorded elsewhere, 32 in Division B and 49 in Division C. 

 Of the 32 species in common with Division B, only two have not been 

 reported from Division C, the Northeast Pacific or the North Atlantic. 

 This bears out the previous statement that the additions to the Gala- 

 pagos fauna, as far as hydroids are concerned, herein listed, reached that 

 region through Division C and not to any extent through Division B. 

 Of the 34 species reported also in the Northeast Pacific and 46 also 

 in the North Atlantic, 25 species are common to both. 



Only five species have been reported from the Pacific south of Peru, 

 and only one of these has not been reported elsewhere. There is a closer 

 relationship between the Galapagos region and Hawaii than between 

 this region and Chili. In the not very extensive collection reported upon 

 by Nutting from the Hawaiian Islands seven species were included that 

 have now been obtained from the Galapagos Islands. Three of these, 

 Acryptolaria pulchella (Allman), Lictorella cervicornis Nutting, and 

 Pliimularia delicata Nutting, may be considered to be definitely oceanic. 



Table II shows the species distribution in the families (18) repre- 

 sented in the collection. In nearly all cases, these families were well dis- 

 tributed throughout the three divisions, and with the exception of two 

 families, each represented by only one species, new species developed 

 during this extension of distribution. 



