IV rREFACE. 



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 specimens, or 

 adds any thing 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 

 characters of the orders, families, minor groups, and species, 

 have been compared and revised with the specimens. In 

 this Part great use has been made of the researches of 

 M. D'Orbigny, who, with the late Baron Ferussac, has been 

 for many years engaged in the study of these animals ; 

 and their works may be considered as the basis of this Part 

 of the Catalogue. 



J. E. GRAY. 



12th February, 1849. 



