OF THE UNITED STATES. 23 



formed of the nummulite limestone, masses of which are 

 scattered in every direction : it is porous, or contains 

 spheroidal cavities, formed no doubt by the decomposi- 

 tion of organic remains, which leave loose casts that are 

 easily washed out by the rains. The most characteristic 

 fossil at this place is Ostrea panda. 



" These limestone hills occur at intervals to the vicinity 

 of Jackson, on the Tombeckbe : on Basset's creek one of 

 these hills rises probably to a height of 300 feet above the 

 w#ter level. I crossed the river at Jackson, which is on 

 a high sloping bluff, entirely diluvial, and proceeded over 

 a succession of pine covered hills until within a mile of 

 St. Stephens, where the limestone again appears. St. 

 Stephens is on a high bluff of this rock, which, wherever 

 it occurs, forms a very broken or undulating surface. A 

 short distance above the village, the bluff rises nearly 

 perpendicular from the river, and is about 100 feet high. 

 Every where in the vicinity this limestone crops out on 

 the summits of the hills, and myriads of Nummulites 

 Mantelli are scattered over the surface of the decom- 

 posing rock. The Qryph&a vomer is occasionally found 

 among them, and the Ostrea panda is abundant, but no 

 other fossils occur excepting what are peculiar to the 

 limestone in question. On the hills I observed the Pec- 

 ten Poulsoni in abundance. Near low water mark in 

 the bluff is a stratum of shells consisting of Ostrea panda 

 and Plagiostoma dumosum, both equally abundant. The 

 surface of this rock is in many places very hard, and of a 

 bluish color, compact, and glittering when fractured, 

 and is convertible into excellent lime. Again it is often 



