250 PALEONTOLOGY OF ILLINOIS. 



In conclusion, it is but justice to ourselves to state, that, however 

 excellent our material has been, the present work has been prosecuted 

 principally during leisure between hours which duty devoted to other 

 palseontological labors little akin to these more special investigations. 

 Tet we would gratefully acknowledge the favorable facilities these same 

 opportunities have placed in our reach, and to which we are more 

 indebted than it were possible to express. It is due to the authorities 

 of the Museum of Comparative Zoology at Cambridge, where we were 

 allowed every privilege it was in our power to take advantage of, to 

 express our deep obligations for opportunities which perhaps are to be 

 found to the same extent in no other quarter for these special purposes. 



