340 SNODGRASS AND HELLER 



Omitting the 2 deep-sea Galapagos species, Galeagra -pam- 

 melas and Pontinus strigatus, of whose distribution nothing is 

 known, the derivation of the fauna of each island or group of 

 islands may be indicated by the tabulation of species on page 



339- 



Of the Revillagigedo fauna, as shown by this table, 12.5 Jo 



is composed of widely ranging species ; slightly less than 50 Jo 

 is American; n ft is Polynesian; about 7 ^ is Eastern Pacific 

 Insular, and nearly 21 Jo is peculiar. 



The peculiar Clipperton species, Ostracion clippertonense is 

 very closely related to O. camurum of the Hawaiian Islands. 

 Hence, of the 9 species known from this island, 4 are of 

 Western Pacific origin. 



Of the Cocos fauna a little less than 50 Jo belongs to the 

 American mainland ; about 30 Jo is Polynesian ; a little less 

 than 16 Jo is Eastern Pacific Insular ; and about $ Jo is peculiar. 



In the Galapagos fauna about 8 ^ is composed of widely 

 ranging species ; slightly less than 47 Jo is American continental ; 

 7 Jo is Polynesian ; 5 Jo is Eastern Pacific Insular ; and 33 Jo is 

 peculiar. 



It is interesting to note that the American faunal element of 

 Cocos Island is much more closely related to that of the Gala- 

 pagos Archipelago than to that of the Revillagigedo Archipel- 

 ago. There are 5 species of this class that occur at the Gala- 

 pagos but not at the Rivillagigedo Islands, while there are no 

 species that occur at Cocos and the Revillagigedo islands and 

 not at the Galapagos. Furthermore, Amia atradorsata and 

 Pomacentrus acrifrons are peculiar to Cocos and the Galapagos 

 islands. Melichthys bispinosus is peculiar to Cocos and the 

 Revillagigedo islands, but is very closely related to the Polyne- 

 sian species M. radula. The Western Pacific fauna of Cocos 

 is about equally distributed between the Galapagos and the 

 Revillagigedo archipelagos. The Galapagos Islands lie in the 

 cold Peruvian current flowing northwest from Cape Horn, while 

 both Cocos and the Revillagigedos lie in the warm equatorial 

 and counter equatorial currents. 



Of the 56 Galapagos species that belong to the American 

 mainland, only 17 occur also at the Revillagigedo Islands. 



