South Dakota School of Mines 123 



exceptional conditions allow for their preservation or petrefac- 

 tion. Turtle eggs are occasionally found filled with hardened 

 mud and eggs of certain extinct birds have been preserved by 

 reason of the thickness of their shells but the Badland birds 

 eggs show not only the thickness of the original shell but also 

 the position of the white and the yolk of the egg. 



One of the Badland eggs found by Mr. Kelly Robinson in 

 1896 has been carefully described by Dr. O. C. Farrington of 

 the Field Museum (see Plate 50). The shell portion is made 

 up of dark colored chalcedony, the color being due to organic 

 matter. The portion representing the white of the egg is gray 

 translucent chalcedony with occasional black blotches the exact 

 nature of which was not determined. The yolk is replaced by 

 opal in two portions of about equal size but with different 

 texture. The egg measures 2.03 inches by 1.49 inches, long 

 and short diameters, conforming in size and general shape to 

 that of the present day Florida duck (Anas fulvigula) * 



Since the publication of the paper by Mr. Farrington I have 

 seen another birds egg from our Badlands, perfect in outline 

 and similar in size and shape to the one described. Others are 

 reported to have been found. 



In addition to the birds eggs several turtles eggs have been 

 found. For a brief description of these the reader is referred to 

 the subject of turtles in this paper. 



•Farrington, O. C. A Fossil Egg from South Dakota. Field 

 -Columib. Mue., Geol. Ser., Vol. 1 189 9, pp. 193-2 00. 2 pis. 



