INTRODUCTION. 
The principal object of the present List has been to give a complete 
Catalogue of the British specimens of Sponges contained in the Col- 
lection of the British Museum, indicating at the same time the pecu- 
liarities of each as regards age, habitation, condition, and the source 
from whence it has been received. 
With this view, the different individuals of each species contained in 
the Collection are indicated by the letters a, b, c, &c., following the 
name of the species and its synonyma, and followed by the habitat, 
state, and the source from whence the specimens were derived. 
Those specimens which have been presented to the Museum have 
the name of the donor ; and in general the collection from whence the 
specimen has been purchased or procured in exchange is also marked, 
as it often gives some authenticity to its history. 
In the adoption of the generic and specific names it has been thought 
right to use, wherever it was possible, that which was first applied to 
the species. As far as regards the specific name, there is comparatively 
little difficulty in the application of this simple rule ; but generic names 
have been used by different authors in senses so widely different, and 
the groups which they were meant to designate have been so variously 
extended and restricted, that it was no easy matter to determine, where 
several names have been used, which of them ought to be preferred. 
Great attention has been paid to consult the original authority, to know 
the type, and select the name which appeared to be the most ancient ; 
and reference is made to the work in which, and the date when, each 
genus and its synonyma were respectively published. 
Under each species there have been appended all the names under 
