SOUTH DAKOTA SCHOOL OP MINES 143 



two and five-eights inches within two inches of the nasal 

 end. The animal in life was perhaps six feet long. The 

 second species, Caimanoidea visheri, found in 1911, shows 

 characters tending toward the alligators. Its length in life 

 was about five and one half feet. 



These fossils are of interest in showing in striking 

 manner the Floridian character of the climate in the White 

 River region during early Oligocene time and they add to 

 other evidence that the country was then a land of inunda- 

 tion. 



BIRDS EGGS 



Several fossil birds eggs have been found in or near the 

 Big Badlands. Unlike eggs found elsewhere as fossils the 

 badland birds eggs are distinctly petrified, that is they show 

 a practically complete replacement of the original matter by 

 mineral material. Soft animal tissues quickly decay and 

 only exceptional conditions allow for their preservation or 

 petrefaction. 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 apparently 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. Farring- 

 ton of the Field Museum. 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). Plate 48.) 



Since the publication of the paper by Mr. Farrington 

 other birds eggs from the Badlands, perfect in outline and 

 similar in size and shape to the one described have been 

 found. One of these is now in the geological museum of the 

 South Dakota State School of Mines. 



