12. L. Hoodie — Mazon Creek Shales. 279 



description, it was thought that it might be of interest to pre- 

 sent a short discussion of these remarkable fossil-bearing beds. 



The writer was enabled to spend a week studying the fossil 

 beds of Mazon Creek last summer with the aid of funds from 

 the Department of Zoology of the University of Kansas and 

 the Elizabeth Thompson Science Fund. It is fitting to express, 

 in this place, to Mr. J. C. Carr of Morris, Illinois, my appre- 

 ciation of the favors shown me while collecting at Mazon 

 Creek. My purpose in visiting the locality was primarily to 

 collect Amphibia, but although several thousand nodules were 

 examined, none contained amphibian remains. Mr. Carr has 

 collected on Mazon Creek for more than thirty years and knows 

 more of the conditions of fossilization and location of the var- 

 ious beds than any one else. It is, however, a significant 

 fact that during all these years of assiduous collecting he has 

 never found an amphibian nor a fragment of one. It was this 

 fact, together with the further one that the Amphibia referred 

 to above represent over sixty years collecting from these beds, 

 which interested me in making the following comparative table 

 of the rarity of the various kinds of organic remains found in 

 these beds. 



If we take 100,000 nodules as a basis for computation of 

 the rarity of the various forms, something like the following 

 will be the approximate result : . 



Of 100,000 nodules, 



20,000 will be barren or contain only indeterminate 



fragments. 

 68,500 will contain plant remains. 

 7,500 will contain insects, Crustacea, myriapods, scor- 

 pions, spiders and other Arthropoda. 

 3,900 will contain fish coprolites or scales. 

 95 may contain fish or fragments of fish. 

 4 may contain molluscs. 

 1 may contain an amphibian. 



Total 100,000 nodules. 



Perhaps even 100,000 is a little low as a basis of estimate. 

 Mr. Carr was of the opinion that one nodule in every 500,000 

 might contain an amphibian. The table given above will, at 

 least, be serviceable in giving an insight into the relative 

 abundance of the various forms. 



The beds where the nodules are usually collected occur along 

 both banks and in the bottom of the creek (figs. 1 to 4) in two 

 localities. 



One locality, known as the Bartlett place, where I camped 

 (fig. 1), is situated eight miles southeast of Morris, in Grundy 

 county, Illinois, Wauponsee township; N. W. quarter section 



