THE NATURAL HISTORY SURVEY 



The report on the paleontology of the area covered by the 

 Natural History Survey will be issued in parts, prepared by 

 Dr. Stuart Weller, of the University of Chicago, and will con- 

 stitute Bulletin No. IV. 



The present report constitutes the second part of this bul- 

 letin and includes descriptions and figures of the Trilobita of the 

 Niagaran limestone of Chicago and vicinity. Nineteen new 

 -species and one new genus are described and figured.. It is 

 noteworthy that about forty per cent, of the species of North 

 American Silurian trilobites have been recognized in the 

 'Chicago area. The description of these, together with the 

 excellent illustrations prepared by Dr. Weller, will furnish a 

 valuable manual on the subject for the use of students in local 

 investigations. 



The territory covered by the Survey includes Cook and Du 

 Page counties and the nine north townships of Will County, in 

 Illinois, with a portion of Lake County, Indiana. This gives 

 .an area of about forty -eight or fifty miles square, or a land sur- 

 face of nearly 1,800 square miles. 



The Board of Managers desires to acknowledge its obligations 

 to the University of Chicago, the Field Museum of Natural 

 History, the Northwestern University, as well as to the indi- 

 viduals whose courtesy to Dr. Weller greatly facilitated the work 

 of preparing this report. Especial mention should be made of 

 the generosity of our patrons, whose continued interest in the 

 work of the Academy has made it possible to issue the present 



