PREFACE. 
The chief objects in forming the present Synoptical Cata- 
logue have been, to exhibit at one view a complete list of all 
the specimens of Mollusca at present in the British Museum 
collection, and to furnish such an account of the species 
known to exist in other collections, but which are at present 
desiderata in the British Museum, as the materials at hand 
would permit me to compile, in order to enable travellers, 
collectors, and others, to assist in completing the national 
collection. 
For this purpose* short descriptions have been given of all 
the genera and species of recent Mollusca at present known 
to exist in the different museums and private collections, 
and of the better-known fossil species of the various families. 
At the end of each description is added an enumeration 
stating the state, age, country, or strata, and other pecu- 
liarities, of each specimen of the kind in the Museum 
collection ; and, when the species is not at present in that 
collection, the museum in which it has been observed is 
often added after the general habitat or locality of the 
species. The different individuals of each species contained 
in the British Museum collection are indicated by the letters 
a, by Cy &c. 
Those specimens which have been presented to the Museum 
have the name of the donor marked immediately after the 
