FRESH-WATER SHELLS. 21 



the fact that LiinncEa trtincatida " has a curious tend- 

 ency to turn up in horse-troughs and stone basins ; " 

 in one instance, he found a number in a raised stone 

 cattle-trough on the marshes of the Humber, where the 

 dykes contained water much too salt for cattle to drink, 

 and a supply had to be provided by deep borings, one 

 of which overflowed from the tube into the trough in 

 question; thus, as he states, "a small colony of L, 

 truncatula was found living in a cattle-trough in the 

 middle of a salt-marsh, where the surrounding dykes 

 were too salt for this snail to live in." ^ In 1890, Mr. 

 C. R. Orcutt recorded the finding of thousands of living 

 Physce in a tank (with a capacity of four thousand 

 gallons) which had been erected, not quite a year pre- 

 viously, by a mining company at Hanlon's Ferry, south 

 of Ft. Yuma, on the west bank of the Colorado River, 

 California. This tank, it is stated, was supplied *' from 

 a six inch well," and " no shells were found alive In the 

 Colorado River only a few hundred feet away." - 



It will doubtless be admitted, as already suggested, 

 that shells found in situations of the present kind 

 (reservoirs, artificially-filled lakes, tanks, troughs, &c.) 

 are in many cases carried in with the supply-water, but 

 it would frequently be found difficult, in individual 

 cases, to ascertain whether a possibility that such 

 is the case really exists. Transportal in this way, 

 to say the least, seems improbable in the three cases 



' C. Reid, "Trans. Norfolk and Norwich Nat. Soc," v. (1892), 

 279. 



- C. R. Orcutt, " Nautilus," iv. (1890). 67-8. 



