]V PREFACE. 



habitat. When there is no such indication, the specimens 

 have been either purchased or procured in exchange ; and in 

 this case, whenever the place or person from whom they have 

 been received gives authenticity to the specimen, or adds 

 anything to their history, they are noted as being from such 

 and such a collection or locality. Great attention has been 

 paid to dates, and the generic and specific names which 

 appear to possess priority in this respect have been adopted. 

 Reference has also been made to the works in which the 

 genera and species appear to have been first described or 

 noticed. 



Catalogues like the present can be little more than com- 

 pilations, and I have freely availed myself of the labours of 

 my predecessors in the same field ; especially of those who 

 have published monographs of the different groups : but the 

 chai'acters of the orders, families, minor groups, and species, 

 have been compared and revised with the specimens. 



J. E. GRAY. 



llth January, 1850. 



