360 EIGHTH PACIFIC SCIENCE CONGRESS 



Recognition of the Indo-West Pacific as a homogeneous faunal 

 region is irrefutable. To this region alone is confined all the Recent 

 sea snakes. Of the 46 Recent species of the coral Fungia only one is 

 found outside the region. Among living molluscs Nautilus^ Hippopus, 

 Tridacna and Malleus are not found elsewhere. Without mentioning 

 specific instances Ekman (1953) refers to many coral and alcyonarian 

 families confined to the Indo-West Pacific, and Myers (1940) recognises 

 many families and genera of fishes not found outside this region. 



The outstanding paleogeographic condition that gave rise to this 

 vast faunal region was undoubtedly Suess' Tethys Sea which allowed 

 almost unimpeded dispersal in the tropical zone. This sea is known 

 to have persisted with but brief local interruptions from the Lower 

 Cambrian to the Tertiary. 



The recognition of the influence of this vast waterway readily dis- 

 solves many otherwise anomalous cases of discontinuous distribution. 

 In molluscs, for instance, the spread to the Austro-Neozelanic provinces 

 in the Tertiary of characteristic Paris and Vienna Basin genera (Eocene- 

 Miocene), such as Baryspira and later Pecten and Ranella, is note- 

 worthy. 



Although the segregation of faunas within the Indo-West Pacific 

 must be of late development a fairly clear segregation is even now ap- 

 parent with endemism strongly marked in areas of continental origin 

 as opposed to the oceanic faunas of islands of coral or recent volcanic 

 origin. 



A false impression of uniformity in the molluscan faunas of the 

 widely scattered insular areas of the Indian and Pacific oceans is given 

 by the extensive distributional patterns of common species of spectacular 

 appearance; i.e. the spotted cowrie Cypraea tigris, and the spider-shell 

 Lambis lamhis. 



In many unrelated tropical gastropod families two efficient free- 

 swimming larval types, known respectively as Sinusigerid and agadinid, 

 are characteristic of most of the Indo-West Pacific wide ranging species. 



It is therefore among the sedentary and less conspicuous elements 

 that endemism is apparent and in the mollusca in particular many 

 regional species and subspecies are apparent. 



Ekman's six divisions of the Indo-West Pacific are in my opinion 

 conservative, and on the other hand the eighteen divisions advocated 

 by F. A. Schilder and M. Schilder (1939) on the basis of a world survey 

 of the Molluscan family Cypraeidae are certainly excessive. Ekman 

 made no reference to this work in his "Zoogeography of the Sea." 



The Schilders advocated the division of the Indo-West Pacific into 

 three "provinces" and eighteen "regions". Their terminology should be 

 reversed of course, i.e. "province" = subregion, and "region" = province. 



