' The Post-Pliocene Non-Marine Mollusca of Ireland.' 163 



nine species — and remark that ' it would thus appear that the 

 German species are not so dominant as Mr. Taylor has assumed.' 



The Western or older group is stated to comprise ' those 

 species which had their origin in Western Europe and have 

 spread eastward,' and these are given as seventy-seven in 

 number. To present date the ' Monograph ' has accurately 

 charted and published the known range of 39 of the yy species 

 mentioned, and from an examination of these distributional 

 maps, it is seen that of these thirty-nine species, only about 

 seven can justly be called strictly Western. None of the 

 remaining thirty-two species are really western, but prepon- 

 deratingly Eastern, Northern or Southern in their tendencies. 



Arion, Limax and Agriolimax, which they state have a 

 decidedly Western distribution, do not show such a character 

 as the published charts will demonstrate. The nine species of 

 Polita are not Western, with the exception of the three species 

 of very doubtful value created by the authors themselves. The 

 two Zonitoides are also not Western, neither can Pyramidula 

 rotundata, P. rupestris, or even Hygromia fusca be claimed as 

 as predominatingly Western. Helix nemoralis and H. hortensis 

 are certainly not Western, nor are Helicigona lapicida and H. 

 arbustorum or Hygromia hispida and H. striolata, while Theba 

 cantiana, T. cartusiana and Helix pisana are preponderatingly 

 Southern. 



None of the remaining thirty-two species are preponderat- 

 ingly Western, and it is not unreasonable to suppose that the 

 distribution of the remaining British species when accurately 

 mapped will show similar proportional results. 



The authors in treating upon the origin of the Irish Mollusca, 

 remark that three theories have been propounded to account 

 for their presence. The first, which the authors term the 

 ' Edward Forbes' theory,' is the belief to which they give their 

 support — with modifications. This theory, propounded by 

 Prof. Forbes, was based upon a study of the Flora and Fauna 

 and of the Palaeontological evidence. 



The second theory, which Kennard and Woodward have 

 dubbed the ' Pan-Germanic theory,' is based upon the study 

 of the Non-Marine Mollusca, and is propounded by the present 

 writer in the ' Monograph of the Land and Freshwater Mollusca 

 of the British Isles.' 



The third theory is characterised as the ' Glacial Exter- 

 mination theory,' and is based upon botanical, palaeo -botanical 

 and geological evidence, and teaches the almost total destruction 

 of the flora and fauna by the climatal severity of the Glacial 

 period. This theory was strongly supported by the late 

 Clement Reid, but is rejected as quite untenable by the authors. 

 i. The second, or as the authors term it, the ' Pan-Germanic 

 theory,' according to them, teaches that the Non-Marine Mol- 



1918 May l.) 



