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, b, c, &c. 



Those specimens which have been presented to the Museum 

 have the name of the donor marked immediately after the 



