Clare Island Survey. 



23 

 LAND AND FRESH-WATER MOLLUSCA. 



By ARTHUR WILSON STELFOX. 

 Plates I. II. 



Read January 22. Published March 7, 1912. 



1. Introduction, 



2. Field- work, 



3. Sub-division of the District, 



4. Comparison of the Sub-districts 



5. Rare Species found in the Distri 



6. The Question of Dispersal, 



7. Influence of Man, 



CONTENTS. 



PAGE 

 1 



3 

 4 

 5 

 7 

 8 

 10 







PAGE 



8. 



Annotated Lists, . . . . 



12 



9. 



Altitudinal Distribution of Species, . 



4S 



10. 



Recent or Holocene Deposits, . 



50 



11. 



Table showing Local Distribution 







of Species, . . . . 



54 



12. 



Bibliography, . . . . 



5S 



13. 



Index of Species, . 



60 



1. INTRODUCTION. 



Carpenter 1 and Praeger, 2 as well as other writers, have pointed out the 

 interest attached to the intermingling and overlapping of northern and 

 southern — Arctic and Lusitanian — species along the west coast of Ireland. 



This is well exemplified in the Mollusca, though it is sometimes difficult 

 to decide to which group a particular species should be referred, owing to the 

 wide range in western Europe that some of these have obtained. Geomalaciis 

 maculosus, Helicella itala, H. barbara, Helix aspersa, Pupa anglica, 3 and P. 

 cylindracea are typical southerners and reach their most northerly stations in 

 the Britannic area. Zonitoides nitidus, Planorbis glaber* Vertigo lilljeborgi, and 

 Pisidium lilljeborgi may be taken as typical of the northern group, the 

 majority of which are partially circumpolar in their distribution or have close 



1 The mingling of the North and the South. Irish Nat., v, 57-68. 1896. 



2 A Tourist's Flora of the West of Ireland. 1909. 



3 Pupa anglica has often been spoken of as a " northern" species, from its frequently inhabiting 

 the northern faces of the cliffs and similar shady habitats, &c. It is, however, a typical Lusitanian 

 and occurs from St. Kilda, off the west coast of Scotland, to Algeria in north Africa, and has its 

 nearest allies on the Atlantic Islands. 



4 Planorbis glaber occurs from northern Europe to the Atlantic Islands and appears to be replaced 

 in Arctic Europe by P. arcticus, in Siberia by P. sibiricus, and in North America by P. parvus. 



A 23 



ii.I.A. in:uc, VOL. XXXI. 



