16 INTRODUCTORY LETTER. 



zeal in procuring for us the productions of the middle 

 regions of North America. 



In my enumeration of the means at my disposal, I 

 have not mentioned the indiWduals who have furnished 

 me with rare specimens, which it would have been very 

 difficult for me to obtain, or who have generally contri- 

 buted to render my work as complete as possible. I shall 

 content myself with citing Professors Van Swinderen of 

 Groningen, Vrolik of Amsterdam, Van der Hoeven, 

 and Van der Boon-Mescii of Leyden, and Dr Hoorn. 

 M. Klinkenberg of Utrecht placed in my power the nu- 

 merous rarities of his Museiim. The Director of the 

 Cabinet of Natural History at Vienna gave me permission 

 to publish the inedited species contained in that Estab- 

 lishment. Dr Thienemann of Dresden gave me about 

 twenty figures of serpents, drawn from the life at Suri- 

 nam, by Dr Hering. Above all, I ought to acknowledge 

 the liberality of Professors Fremery and Lith de Jeude 

 of Utrecht : these philosophers were so obliging as to per- 

 mit me to select specimens from the valuable collection 

 of Reptiles confided to their care, most of Avhich are na- 

 tives of Ceylon, the coast of Guinea, North America, &c. 



I was about to terminate my work, when, at the end of 

 a long illness, I had the honour, Sir, to accompany you 

 in a journey to Paris, and across a part of Germany. The 

 great number of objects which I saw during this journey, 

 have obliged me to make several additions to my work ; 

 additions, however, which would not have been very im- 

 portant, if I had not been permitted to examine, at my 

 leisure, objects in themselves rare, or partly new. I owe 

 this privilege to the extreme politeness of various philo- 

 sophers who are at the head of scientific establishments : 

 MM. Duvernoy at Strasburg, and Cretzschmar at Franc- 

 fort, were anxious to afford me a free use of the collections 

 confided to their care. M. RUppell, whom I have the 

 advantage of acknowledging among my friends, has fur- 

 nished me with observations on the various reptiles which 

 he had an opportimity of examining in his two voyages ; 

 and, lastly, the observations of several amateurs of Paris, 

 among whom I especially mention Dr Cocteau and M. 



