8o 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



different forms is possible ; and without this knowledge the study of 

 geographical distribution is useless. Fischer, in his 'Manuel de 

 Conchyliologie ' (p. 196), has adopted regions corresponding with 

 those of Sclater and Wallace, except that a Neantarctic is sepa- 

 rated from the Neotropical. So far, however, as the operculated 

 Gasteropoda are concerned (and their affinities are far better 

 ascertained than those of the Pulmonata), I cannot see the least 

 resemblance in many cases to the distribution by regions of mam- 

 mals and birds. I will only notice one case. The OyclojphoridcB 

 (with one genus of Helicinidce and one of Cyclostomatidce) of New 

 Guinea and the neighbouring islands, so far as they are known, 

 appear to differ from those of Borneo much as the latter do from 

 those of Ceylon, as will be seen by the following lists of genera 

 represented, compiled mainly from Pischer's : — 



Operculated Land Mollusca. 



New Guinea and 

 neighbouring islands. 



Pterocyclus. 



Cyclophorus. 



Leptopoma. 



Cyclotus, 



Diplommatina. 



Leucoptychia. 



Pupina. 



Pupinella. 



Callia. 



Helicina. 



Omphalotropis. 



Borneo. 



Pteroc5'cIus, 



Opisthoporus. 



Cyclophorus. 



Leptopoma. 



Cyclotus. 



Diplommatina. 



Opisthostoma. 



Megalomastoma. 



Alyeajus. 



Pupinella. 



Phaphaulus. 



Helicina. 



Phaneta. 



Omphalotropis. 



Ceylon. 



Pterocyclus. 



Aulopoma. 



Cyclophorus. 



Leptopoma. 



Cyathopoma. 



Diplommatina. 



Cataulus. 



It is true that our knowledge of the Papuan mollusca is very 

 inferior to that of the Bornean and Ceylonese, especially the latter ; 

 but sufficient is known to show that the three belong to one region 

 as regards operculated land-shells. The same is the case with Nor- 

 thern Australia. It is scarcely necessary to point out that between 

 the mammalia of Australia with New Guinea and those of Borneo 

 or Ceylon there is the greatest difference. 



The distribution of land-plants into six regions of approximately 

 equal value has never, I believe, been accepted by any botanist. 

 All schemes of repartition with which I am acquainted differ widely 



