Quarterly Journal of Conchology, 267 



point of recording the fact, but, after a little deliberation, I 

 resolved not to do so, as I felt convinced that it was not indigen- 

 ous to, but had been introduced, and that very recently, into 

 Guernsey. 



To this conclusion I v\-as led (i) because all the specimens I 

 found were adults — not a single individual with a mouth un- 

 finished was to be seen, after several days of diligent searching, 

 and (2) their habitat was so circumscribed, and their number so 

 sm.all — not exceeding, probably, a few hundreds — that I was 

 driven to the conclusion that they could not possibly have existed 

 there for any great length of time. The position of the spot, too, 

 was remarkable, inasmuch as it had a uorth-eastcrn aspect. 



In " British Conchology," vol. i, p. 208, Dr. Gwyn Jeffreys 

 observes that "the limited range of this species in Great Britain 

 is remarkable," and adds that two attempts he made to colonize it 

 on the sand hills near Swansea proved altogether unsuccessful. 

 Now, in the autumn of 1S74, being in that neighbourhood, I 

 visited the spot for the express purpose of discovering, if possible, 

 some trace at least of Dr. Gwyn Jeffreys' industry, and, to my 

 astonishment, and to his also — for I immediately informed him of 

 the fact — I found the shell in countless numbers, of all ages, the 

 variety alba having apparently the superiority as to numbers. 

 From these facts we may infer that Pisaua is, under favourable 

 circumstances, capable of colonization, that the immigrants, 

 from some cause (the sudden cliange, perhaps, injuriously 

 affecting their delicate constitution) do not long survive, but leave 

 behind them a progeny which, being born there, take more kindly 

 to the place. This may, in some measure, explain how it was that 

 Mr. S. Tye found all the young specimens in Vazon Bay feeding 

 in the open, while the old ones (which were probably sickly) had 

 gone for shelter to the brick wall. 



