VI 



genera described in Part II, Section 3, bear the date of 1889, 

 which, as it now happened, is apparently a case of antedating. 

 However, as all the new species in the volume were recorded in 

 Mr. S. A. MILLER'S "Korth American Palaeozoic Fossils," which 

 work was published in November, 1889, this may be taken as 

 an excuse for omitting corrections of the above dates, in the 

 "Errata." 



The plates illustrating Part II, were printed before Prof. 

 WORTHEN'S deach. Mr. CHAS. K. WORTHEN made the origi- 

 nal drawings for plates IX-XXV1II, the remaining 58 were drawn 

 by Mr. E. 0. ULRICH, who also contracted for and lithographed 

 all the 78 plates. The KREBS Co. did the printing. Mr. ULRICH 

 informs me that a strike among the pressmen, and the conse- 

 quent necessity of employing inexperienced hands hi printing 

 plates XXXVIII-LX, was the cause of the less satisfactory ap- 

 pearance of these plates. 



As this volume not only forms the final report of the Geo- 

 logical Survey of Illinois, but also represents the last work of 

 its venerable Director, it seems appropriate to close these eight 

 volumes with a biographical sketch and portrait of Prof. 

 WORTHEN, and to add a general index to the entire series of 

 his reports. 



Mr. N. W. BLISS, Attorney at Law, a near relative of the de- 

 ceased and his most intimate friend from childhood, was re- 

 quested, at the suggestion of Prof. WORTHEN'S family, to sketch 

 his private life, and Prof. C. A. WHITE, M. D., of the United 

 States Geological Survey, to likewise treat the scientific work of 

 Prof. WORTHEN, and both of them willingly responded. Their 

 sketches will be found in the "Appendix." 



It is my pleasant duty hereby to render thanks officially to the 

 heirs the 6 sons of Professor WORTHEN, who defrayed all ex- 

 penses for the excellent portrait of their lamented father, which 



