8 THE DISPERSAL OF SHELLS. 



the marshes of the Ouse, distant seven furlongs. Noted 

 June, 1890. The species observed were /./;//;ztip<i;/^;'^^r<^, 

 Ranunculus aquatilis, and Elodea. 



(3). " Small pond by the side of the high road, half a 

 mile west of Christ Church, Stansted (near the Hamp- 

 shire border) ; height, 312 feet above the sea, and 220 

 feet above the nearest stream ; nearest water a small 

 stream, distant about two miles to the south-south-west, 

 but apparently containing neither of the plants found in 

 the pond. Noted September 25th, 1891. The species 

 found were Liniuma peregra^ Planorbis spirorbiSyPotauio- 

 gcton natans, Zannichdlia palustris^ all abundant ; the 

 two plants in fruit, and carrying many eggs of Liimifea. 

 ZajinicJicllia occurs again in a pond in a brick-field, two 

 miles to the south-west, but does not fruit there ; the 

 nearest natural station for it seems to be in the slightly 

 brackish marshes near Emsworth, four miles to the south. 

 Potamogeton natans can probably be found within three 

 miles. This pond is overshadowed by a large oak, and 

 supplied by dew and rain off the road ; neither of the 

 plants, however, is a species likely to be brought to the 

 locality by carts or on the hoofs of horses." 



The absence of bivalves from such ponds, it is true, 

 need hardly be regarded as surprising, but I am unable 

 to agree with Mr. Reid in thinking that the occurrence 

 of the smaller kinds in isolated waters is likely to be 

 altogether exceptional. The creatures may easily be 

 overlooked, and Mr. Reid tells us, in the paper just 

 quoted, that he " could only stay to note the common 

 and conspicuous animals and plants." The catch-water 



