DISTRIBUTION. 



257 



Doubtful, Southern Pacific? 



Isop.s imperfecta 

 Geodia inconspicua 



South Sea. 

 South Sea. 



Three of the six genera of the Pacific Geodidae, Caminella, Caminus, and 

 Isops, have been found only in the western and northwestern Pacific, on the 

 coasts of eastern Austraha and Asia and of the eastern Asiatic Islands; one, 

 Geodinella, only in the northern Pacific, on the coast of Japan, and the northern 

 part of the west coast of North America. The other two, Sidonops and Geodia, 

 are more widely distributed, and the latter (Geodia) represented in every one of 

 the eleven areas distinguished above. 



The number of species of Geodidae found in the northern half of the Pacific 

 is very much greater than that of its southern half. Although this difference is 

 no doubt to some extent due to the inferiority of our knowledge of the latter 

 compared to the former, I think that it may also, in part, be ascribed to a real 

 relative paucity of species in the southern half of the region. 



Within the eleven areas distinguished above some species, notably the 

 western Geodia herryi and the eastern G. ogassizil, are very widely distributed. 

 The latter, which I was able to study carefully, exhibits very considerable differ- 

 ences in the specimens from the most distant localities. This, and the fact that 

 the Pacific species of Geodidae differ from the ultra-Pacific species and that 

 none of them occurs in more than one of the eleven areas distinguished, seem to 

 indicate that these sponges are unable to retain their characters fairly un- 

 changed when dispersed over extensive areas. 



