NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 25 



Paludina vivipara (L.). 



Locally abundant. 



Vivipara costse Heldreich. 

 Paludina Duboisiana Mousson. 

 Paludina subfasciata Bourg. 



The V. costce described by Heldreich from Turkey would 

 appear to be referable to this species. Dr. Kobelt also refers 

 to its synonymy, Paludina Duboisiana Mous., and Palicdina 

 subfasciata, Bourg. 



Lovell Reeve regards, we think erroneously, the Vivipara 

 contectoides of Binney, a native of the United States, as a variety 

 of this species " lighter and more inflated in growth." It ap- 

 pears to us to have more affinity with P. contecta Millet. It is, 

 however, but right to add that most authors prior to Binney 

 were of the same opinion as Mr. Reeve. 



The Rev. W. C. Hey, M.A., of York, records the effect of 

 sudden frost upon the species when left unexpectedly exposed on 

 the bank. " On January 19th, 18S0, the Ouse at York was 

 considerably lowered by opening Naburn Lock, and a very 

 large number of freshwater shells were consequently left on the 

 banks. A hard frost set in the same night (the thermometer 

 registering eight degrees of frost), and continued till the lock 

 was closed. The mud banks became perfectly hard to the 

 water's edge, and Paludina vivipara, which occurs in great 

 abundance, was unable to resist the frost in spite of its opercu- 

 lum and thick mud coat. All the specimens I examined were 

 dead. Some had made a futile attempt to bury themselves, but 

 as they live in a stony part of the river, they had not a fair 

 chance." Mr. Hey infers that this species lives too deep to be 

 accustomed to a temperature below thirty-two degrees. 



M. Joly has recorded that he has submitted this species 

 to a temperature of 23° Fahr., after keeping them without food 

 for three months, and on dissolving their icy prisons found 

 them all still living. 



