ZOOGEOGRAPHY. 149 



such typical recent families as Helicidae and Bulimulidae, and others, which are 

 the \ery families known to be most successful as emigrants; for species of these 

 modern successful families follow modern agriculture and commerce about the 

 world, and easily become established. Some of these have come to Polynesia 

 within historic times; but we find none existing as a part of the true fauna of 

 any island. Thus Pilsbry continues, "the advocate of a Polynesian waif fauna 

 is then compelled to adopt the view either that accessions to the mid-Pacific 

 snail faunas practically stopped a long time ago, from causes unknown or hypo- 

 thetical, or that an unparalleled series of accidents intervened to pre\'ent the, 

 in recent times, ubiquitious and prominent continental groups of snails from 

 effecting a landing in these islands." In continuing he shows how wrong 

 Wallace was in deri^•ing the Polynesian fauna from the Australian region, and 

 says: "Far from being a faunal dependency of the Austrahan or Oriental regions, 

 Polynesia has every appearance of being a region which started with a fauna 

 long antedating the present Australian and Oriental faunas, developing along its 

 own lines, retaining old types because they did not come into competition with 

 the higher groups developed on the greater and less isolated continents * * * 

 On the supposition that Polynesia has always had the constituti(5n the name 

 implies, it is difficult to see why agencies which introduced representatives of 

 some eight families of snails into the Hawaiian group should totally fail to act 

 during the mesozoic and tertiary. Even Wallace felt that some explanation 

 was called for, and speaks vaguely of the ' extensive shoals to the south and south- 

 west,' and 'two deep submarine banks in the north Pacific between the Sandwich 

 Islands and San Francisco.'" Again Pilsbry says, "In writing that 'none of 

 these oceanic archipelagos present us with a single type which we may suppose 

 to have been preserved from mesozoic times' (I. c, p. 305), Wallace makes a 

 statement totally at variance with the nature of their land molluscs." Cramp- 

 ton has told me that he has arri\'ed at similar views by studying the Partulae of 

 Tahiti and other islands where they occur. 



These quotations are made here simply to show how an opinion, almost 

 universally held at one time, has had to give way to the newer interpretation of 

 conditions in the Polynesian Islands based upon fuller collections and a better 

 knowledge of palaeontology. 



In the East Indies the islands have always been considered to be of conti- 

 nental origin; so that the question is not one of whether the islands have e\er 

 been connected with one another, and with the mainland, but rather one of the 

 exact conditions as regards land-bridges and their positions. Scharff, in his 



