INTRODUCTION. 
The principal object of the present Catalogue has been to give a com- 
plete List of the British Specimens of Radiated Animals ( Centronics ) 
contained in the Collection of the British Museum, indicating at the 
same time the peculiarities of each as regards age, habitation, con- 
dition, 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 synonvma, and followed by the habitat, 
state, and the source from whence the specimens are 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, where- 
ever 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 manners so widely different, and the groups which 
they were meant to designate have been so variously extended and re- 
stricted, 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 
svuonyma were respectively published. 
