IV INTRODUCTION. 



of moment to their history, they are noted as being from such 

 or such a collection. 



In the adoption of generic and specific names, it has been 

 thought right to use, whenever it was possible, that which was 

 first applied to the species. As far as regards the specific 

 names, there is comparatively little difficulty in the applica- 

 tion of this simple rule ; but generic names have been used by 

 different authors in senses so widely different, and the groups 

 which they were meant to designate have been so variously 

 extended or restricted, that it is no easy matter to determine, 

 where several names have been used, which of them ought to 

 be preferred. And as every original observer will constantly 

 make use of characters which others may have overlooked, or 

 not thought of so much importance as he may be inclined to 

 attach to them, even when a generic name is used, it will of 

 necessity be often employed in a different sense, or with a 

 more restricted or extended meaning than its original proposer 

 applied to it. 



It is needless, however, to enter into the details of nomen- 

 clature, further than to observe that to the name adopted for 

 the genus is appended the specific name under which the ani- 

 mal is believed to have been first described. If the generic 

 name adopted be different from that employed by the esta- 

 blisher of the species, his name immediately follows it as a 

 synonyme ; and where the animal has received more than one 

 specific name, these names are also given. But it has been 

 thought unnecessary to load the Catalogue with any other ge- 

 neric names, where no change has been made in the specific, 

 as it has been considered that these names will be sufficient 

 for all the purposes of identification. 



In those cases where the two sexes of the same specie?, or 

 any particular individual state or variety belonging to it, has 

 been differently named, such names (belonging exclusively to 

 the state or individual so described) are placed after the refe- 

 rence to the specimen to which they generally apply. 



To determine with accuracy the names and synonymes of 

 the species, the Museums of Paris, Leyden, Vienna, Berlin, 

 Francfort, &c, have been personally examined. Many of the 

 specimens in the Museum collection have been received from 

 the origiual describers, and most of them have been examined 

 by M. G. Bibron, one of the authors of the Erpetologie 



