II SHOWERS OF SIIKLLS 47 



Writing to the Zoological Society of London from Now 

 Caledonia, Mr. E. L. Layard remarks : ^ " The West Indian 

 species Stenoyyra octona has suddenly turned up here in 

 thousands ; how introduced, none can tell. They are on a 

 coffee estate at Kanala on the east coast. I have made in- 

 quiries, and cannot find that the planter ever had seed coffee 

 from the West Indies. All he planted came from I>onibay, and 

 it would be interesting to find out whether the species has 

 appeared there also." 



Sometimes a very small event is sutlicient to disturb the 

 natural equilibrium of a locality, and to become the cause either 

 of the introduction or of tlie destruction of a species. In 1883 

 a colony of Helix seric.ea occupied a portion of a hedge bottom 

 twenty yards long near Newark. It scarcely occurred outside 

 this linut, but within it was very plentiful, living in company 

 with H. nemoralis, H. liortensis, H. hisinda, H. rotundata, Hyalinia 

 cdlaria and Sy. nitidida, and Cochlicopa luhrka. In 1888 the 

 liedge was well trimmed, but the bottom was not touched, and 

 the next year a long and careful search was required to find 

 even six specimens of the scriccar 



Showers of Shells.- — Helix viryata, H. caperata, and Coclili- 

 ■cdla acuta sometimes occur on downs near our sea-coasts in such 

 extraordinary profusion, that their sudden appearance out of 

 their hiding-places at the roots of tlie herbage after a shower of 

 rain has led to the belief, amongst credulous people, that they 

 have actually descended with the rain. There seems, however, no 

 reason to doubt that ]\IoIlusca may be cauglit up by whirlwinds 

 into the air and subsequently deposited at some considerable 

 distance from their original habitat, in the same way as frogs 

 and fishes. A very recent instance of such a phenomenon 

 occurred ^ at Paderborn, in Westphalia, where, on 9th August 

 1892, a yellowish cloud suddenly attracted attention from its 

 colour and the rapidity of its motion. In a few moments it 

 burst, with thunder and a torrential rain, and immediately after- 

 wards the pavements were found to be covered with numbers of 

 Anodonta anatina, all of which had the shell broken by the 

 violence of the fall It was clearly estal)lished that the shells 



1 P. Z. S. 1888, p. 358. - W. A. Gain, Naturalist, 1889, p. 58. 



* Das Wetter. Dec. 1892. Another i,ase is recorded in Amrr. Nat. iii. p. 



