Sechellea and Amirantes Islands. 65 



the energy to reside for many years in places purposely se- 

 lected on account of the great abundance of molluscous animals 

 which they afford ; and the places most favourable for the 

 multiplication of these animals, be it remarked, are commonly 

 most remote from human habitations, especially from the ha- 

 bitations of civilized man ; and this circumstance renders great 

 devotion to the subject, and also considerable expense, requi- 

 site, in order to obtain the opportunities most favourable to 

 observation. 



With this object in view, M. Dufo, induced by his love for 

 conchology more than any thing else, and with no other mis- 

 sion than the desire to be useful, took up his residence among 

 the Sechelles and Amirantes Islands, which present a great 

 number of creeks and rocks, sandy flats and shoals, which 

 are but rarely visited by navigators. Taking along with him 

 a few negroes and suitable provisions, he could here deliver 

 himself up, without fear of interruption, to long and repeated 

 observations on many points in the natural history of the con- 

 chyliferous moUusca, and among others the operculum, and 

 the different modifications through which shells pass from 

 youth to their decline. 



The first point, so long neglected, to such a degree, indeed, 

 that the study of it may be said to have commenced in our 

 days, and, in the works of one of the present reporters, has ac- 

 quired great importance since it has been demonstrated that 

 it may be employed not only for the distinction of species of 

 which we possess only the shell, but for confirming truly na- 

 tural generic groups. M. Dufo has established, in regard to 

 a great number of species of the genera Fusus, Turbinella, 

 Murex, Purpura, Buccinum, &c. that this view of the matter is 

 correct. Thus, he has shewn by the operculum of the so-called 

 Buccmum undosum^ that it is a species of the genus Turbinella, 

 and by that of Cerithium palustre^ which differs, by the composi- 

 tion of the imbricated circular elements, from that of the true 

 Cerithiums, that it does not belong to this genus. In like manner, 

 he has confirmed the genus Potamides, established by M. Alex- 

 ander Brongniart, for the fossil shells regarded before his time 

 as Cerithiums, and which the fluviatile naturp of the locality in 

 which they are found, as well as some peculiarities in the form 



VOL. XXIX. NO. LVII. JULY 1840. B 



