176 THE ZOOLOGIST. 



this trio, that, failing anatomical differences, they are probably 

 only varieties of well-known species. Helicella heripensis is 

 apparently very near to the variety gigaxii of H. caperata ; 

 Planorbis vorticulus is perhaps an almost keel-less form of 

 P. vortex (it had been recorded from Pleistocene deposits in the 

 county some years before it was discovered in the living state) ; 

 and Valvata macrostoma is still considered by some authorities to 

 be identical with the variety depressa of V. piscinalis. 



Lusitanian Elements. 



Animals and plants which are supposed to have reached 

 Britain from the Continent by land connection to the south-west 

 of Ireland in Miocene times constitute the so-called Lusitanian 

 element of our fauna and flora. Dr. Scharff remarks that 

 though we have a good many species of Lusitanian origin in 

 the British Isles, yet " we have only a mere remnant of what we 

 ought to have, had the climate been less trying. . . . That 

 the Lusitanian fauna is very ancient in the British Islands is 

 proved by the fact of the discontinuous distribution of so 

 many species. A greater number survived in Ireland than in 

 England." * 



In Sussex the Lusitanian elements of our molluscan fauna 

 include Helicodonta obvoluta, which still lurks in the recesses of 

 the primeval woodland tracts on the slopes of the Downs and in 

 ancient parks ; Helicella cartusiana, another downland species 

 occurring in isolated colonies ; and Hygromia fusca, a woodland 

 species of great rarity. There are indications that these elements 

 are waning. Dead shells of Helicodonta obvoluta occur in spots 

 where repeated search has failed to yield the living animal. 

 Helicella barbara (= Helix acuta) at one time flourished at Mill 

 Gap, Easebourne, but is now extinct there. Three specimens of 

 Helix pisana from the collection of the late Frederick Townsend, 

 F.L.S. (now in the Haslemere Museum), are said to have been 

 found in Sussex about the middle of the past century ; further 

 evidence of the existence of this species in the county is very 

 desirable. Precise information concerning the distribution of 

 Helicella cartusiana is needed ; the records appear to indicate 

 that it is dwindling. 



* 'History of the European Fauna,' p. 307. 



