Irbdale. — Mollusca of the Kermadecs and Norfolk Island. 507 



scriptions and figures, none of these can be referable to Charopa as now 

 understood, and they can only be considered as very doubtful constituents 

 of the Norfolk Island fauna. 



VI. Review and Conclusions. 



The conclusions to be drawn from these digests can now be summarized, 

 and strongly indicate the different origin of the land molluscan faunas of 

 the two groups. Whereas the Kermadec series alone did not tell much, 

 when contrasted with the Norfolk Island collection quite a deal can be 

 determined. The apparent source of the Kermadec molluscs is Polynesia, 

 the Neozelanic element being quite probably also of that origin, having 

 arrived from the north. It might here be observed that whilst the Endo- 

 dontidae have been sometimes claimed as an Antarctic group, equally strong 

 claims have been made for their northern origin. Two masters in the 

 science of drawing deductions from observations made on the distribution 

 of land molluscs have differed on this point. I would suggest that corre- 

 lation might be brought about were restricted groups utilized. As far 

 as my own observations have yet proceeded, I find groups giving an Ant- 

 arctic range, whilst other groups as surely show a northern origin. Thus 

 in the Kermadecs the " Thaumatodon " group emphasizes a northern 

 source, whilst just as surely the "' Discocharopa " group suggests a southern 

 origin. I hope to deal with such questions in more detail later, giving 

 facts in support of these suggestions. 



The most casual examination of the Norfolk Island land Mollusca pro- 

 hibits any idea of the attachment of this fauna to that of New Zealand. 

 The preponderance of Zonitoids and the scarcity of " Endodonts " are 

 equally assertive, whilst the nature of the Zonitoids suggests at once Fiji 

 as a source of supply. The lack of Placostylus is somewhat extraordinary, 

 whilst, though no species on the Fijian Group recalls Advent), it must be 

 remembered that the Fijian Group has also suffered such vicissitudes as 

 would easily account for the extinction of its relations, if any ever existed 

 there. The presence 'of a subfossil inseparable in shell characters from 

 the Fijian genus Fretum is noteworthy, especially as there appears little 

 doubt that Belloconcha is a closely allied genus. This genus would seem 

 to have been the predominant Norfolk Island mollusc, though now Fanulum 

 appears to have taken this place. The extraordinary Roybellia, I have 

 suggested, may be allied to Fanulum. The exact relationships of the other 

 Zonitoids is difficult to suggest, as so little is known of the Polynesian 

 minutiae. The Microcystine genera Greenwood ocotichn and Allenoconcha are. 

 certainly closely allied to " Microcystis " and the varied Polvnesian shells 

 commonly known under that genus-name. The Omphalotropis, Palaina, 

 and Nesopupa are very closely allied to Fijian and other Polynesian species. 

 Indeed, I suggest that longer series from other localities would cause their 

 degradation to the rank of subspecies only. 



Though Norfolk Island is situated somewhat midway between New 

 Caledonia and New Zealand, and in recent charts soundings show the 

 presence of a submerged ridge connecting the three, the land molluscs 

 prohibit any direct connection between the three, whilst they just as surely 

 point to a junction in some way or other with the Fijian Group. I make 

 this reservation as, though Placostylus has reached that group, it has not 

 been found Recent or fossil on Norfolk Island. 



Though I have not introduced any mention of the Lord Howe Island 

 land Mollusca, I would simply note that Hedley pointed out these were 



