PREFATORY REMARKS. 



IT is now exactly thirty years since I commenced to collect (in 

 the autumn of 1847) the Land-Shells of the various outlying 

 islands and rocks of the Madeiran Group ; and although Insects, 

 rather than Mollusca, formed at that time the main object of 

 my researches, I was nevertheless enabled to add a considerable 

 number of unmistakeably new species to the careful and elabo- 

 rate catalogue which had previously been compiled by my excel- 

 lent friend, and after-companion, the late Eev. K. T. Lowe. Not 

 10 mention the many explorations and encampments which I 

 subsequently enjoyed in Mr. Lowe's company during four suc- 

 cessive trips to the archipelago, the last of which occupied the 

 summer of 1855, it was not until January of 1858 that the 

 liberality of John Gray, Esq., gave me the first opportunity of 

 turning my attention to the Canarian fauna. 



By a somewhat curious coincidence Mr. Lowe was at that 

 particular time spending the winter in Teneriffe, so that Mr. 

 Gray's yacht was generously placed at our disposal to visit the 

 numerous islands of the widely-scattered Canarian Group ; and, 

 although Mr. Gray's sojourn was unexpectedly curtailed, I did 

 not return to England until the following July, and with the 

 full intention, even then, of making a second expedition so soon 

 as the necessary arrangements could be completed. This, for- 

 tunately, did not require long ; for I again had a very profitable 

 interval, from February to July of 1859, in the Canarian archi- 

 pelago, joined, as before, by Mr. Lowe. 



Seven years now elapsed, during which I was completely 

 taken-up by the working out of the material which had been thus 



