FRESH-WATER SHELLS. \J 



across, and for miles there was no natural surface water.^ 

 Liinncza macrostoma, according to Dr. Ingalls (who 

 communicated the fact to Mr. Binney in i860), not seen 

 elsewhere within twenty miles, seems to have suddenly 

 appeared in a pool, about twenty feet in diameter 

 (entirely cut off from streams and fed by a spring), 

 which had for years been frequented by the observer for 

 Desmidia, &c. ; this, he added, '' comes as near a case of 

 spontaneous generation as anything within my observa- 

 tion." ^ The Rev. James Dalton, in 1861, mentioned 

 the finding of a dozen species of shells in a pond at 

 North Stainley, near Ripon, at least half a mile from 

 any other water, and two of these, Linincea stagnalis 

 and Cyclas caliculata^ [= Sphceriuvi lacustre\ did not, 

 as far as was known, occur elsewhere in the neighbour- 

 hood.^ The occurrence of shells in the isolated waters 

 of pits, quarries, brick-yards, &c., is notorious ; Mr. 

 Standen tells me, for instance, that some recently ex- 

 cavated " brick pits " at Cheetham Hill, near Man- 

 chester, though far from other ponds, swarm with 

 common molluscs, Sphceriuin corneiun^ Pisidiuin fon- 

 tinale, Linincea peregra, Limncea truncatida, LimncBa 

 stagnalis, &c. The presence of A nodonta fluviatilis'm num- 

 bers in a hole, south of Dover Plains, Eastern Duchess 



1 " West American Scientist" (C. R. Orcutt, editor), i. (1885), 



74. 



' W. G. Binney, '• Land and Fresh-water Shells of North 

 America," part 2 (1865), p. 37, " Smithsonian Miscellaneous Col- 

 lections," vii., 1867. 



^ J. Dalton, "Zoologist," xix. (1S61), 7318-9. 



C 



