ALIEN MOLLUSCA IN YORKSHIRE. 



J. A. HARGREAVES and J. DIGBY FIRTH, F.L.S. 



From time to time various records of alien mollusca in the 

 county have been made in different magazines. In 1885 a 

 Uving Helix lactea was obtained at Pateley Bridge ; several 

 different genera have been obtained at Hull from ships bringing 

 cattle bones and other goods, but we have not been able to 

 find records for Yorkshire of living molluscs having been 

 imported with grain, though frequent mention occurs in isolated 

 paragraphs of specimens imported with currants, bananas and 

 other fruits and vegetables both in Yorkshire and elsewhere ; 

 while Mr. J. W. Clarke has shown Helicella capcrata taken 

 from the feathers of an immigrant bird immediately after 

 landing on the East Coast. 



Further records are given in Kew's ' Dispersal of Shells.' 

 Living specimens of foreign helices were obtained by us from 

 the vicinity of Wakefield, and subsequent search resulted in the 

 production of over 100 specimens, of which about one third 

 were alive when procured. They were obtained from barley 

 ' screenings ' and were accompanied by large numbers of 

 seeds of alien plants, the growths from which have been ex- 

 amined by the Leeds Naturalists, a detailed record having 

 been made. In the screenings were also found many more or 

 less fragmentary specimens of Tenebrionidae, mostly alien 

 species of Blaps. 



Careful search was made on more than one occasion to see 

 if any of the molluscs were able to establish themselves in the 

 neighbourhood. Most of the screenings were deposited on the 

 sloping banks of a large deep pond in a disused quarry, and here 

 also several living specimens were obtained, along with many 

 dead shells. Poultry had free access to the rubbish heap, and 

 apparently only a few molluscs escaped their vigilance. In 

 this district where the soil is not calcareous, poultry are natur- 

 ally keen on the shells of molluscs, and in one place where the 

 screenings had been levelled, and afforded a better opportunity 

 for seeing them, scarcely a vestige of a shell was to be seen, 

 showing how closely the mass had been scrutinised by the 

 birds. It appears fairly certain that there is very little proba- 

 bility of the molluscs establishing themselves in the neighbour- 

 hood unless protected from capture by birds. 



Mr. J. E. Crowther of Elland has obtained a number of 

 molluscs from imported barley when it was being steeped, the 

 snails rising to the surface. His commonest shell, as at Wake- 

 field, was Helicella pyramidata, which comprises over two 

 thirds of the specimens. 



It is perhaps advisable to place on record the species 

 obtained. For the identifications we are indebted to Mr. J. 



1918 Aprill. 



