INTRODUCTION. 



The Joint Committee of the Library of Congress entered into an 

 engagement with the undersigned, in 1851, to prepare the Report 

 upon the Herpetological collections made by the United States Ex- 

 ploring Expedition. Finding that other duties would interfere with 

 the proper performance of the work, he was permitted to associate 

 Dr. Girard with him in its execution ; by whom the determinations 

 and descriptions have been made, the drawings overlooked, and the 

 work carried through the press. 



S. F. BAIRD. 



WAsmNGTON, Maj, 1858, 



