GEOLOGICAL SOCIETY. 



67 



portions of the great valley of the Mississippi river, 

 in the cavernous limestone, which here constitutes 

 the surface rock for hundreds of miles. Some of 

 these caverns, such as the mammoth cave of Kentucky, 

 are several leagues in extent, and appear to have once 

 been the channels of subterranean rivers, a circumstance 

 which may possibly explain the comparative rare oc- 

 currence of organic remains within them. 



Nitre, or saltpetre, is not unfrequently found adher- 

 ing to the surfaces, and in the soil of clay, mud, or 

 stalagmite formed at the bottom. The cave in Green- 

 briar county, Virginia, in which the Megalonyx bones 

 of Jefferson were found, is thus situated, and was for- 

 merly extensively worked for saltpetre ; the bones were 

 buried two or three feet beneath the surface of the floor 

 of the cave ; they are completely fossilized, very dense 

 and heavy, of a white color, and are still very well pre- 

 served. 



Megalonyx laqueatus. Harlan. 



Journal of the Academy of Natural Sciences of Philadelphia, vol. vi. p. 269 

 PI. 12, 13, 14. Also, in the American Monthly Journal of Geology and £j"a- 

 tural Sciences, 1831 and 1832. "Description of the jaws, teeth, and clavicle 

 of the Megalonyx laqueatis" By R. Harlan, M. D. vol. i. p. 74. PI. 3. 



Locality. " White Cave," Edmondson county, 

 Kentucky, on the southern bank of Green river, fifty 

 miles in a direct northern line from the Ohio river, and 

 about half a mile from the mouth of " Mammoth Cave. ?? 

 The specimens of this highly important organic re- 



