CHAP. XXXV.] FOSSIL CORAL REEF. 277 



I had found this ledge, both at Mount Yernon and 

 at Evansville, to contain land and freshwater shells, 

 At the last-mentioned town, where the terrace was 

 from twenty to thirty feet high, one of the lower 

 beds of coarse materials was full of Paludina and the 

 valves of a Unio, both of living species ; yet with 

 them were included, in the same gravelly and shelly 

 mass, the well-preserved bones of the megalonyx. 



The coal-measures had given place to an older 

 series of strata, the Devonian, when we reached the 

 Falls of the Ohio, at Louisville, where are saw the river 

 foaming over its rocky bed. I first landed at New 

 Albany, in Indiana, nearly opposite Louisville, that 

 I might visit Dr. Clapp, and see his splendid collec 

 tion of fossil corals. He accompanied me to the bed 

 of the river, where, although the water was not at 

 its lowest, I saw a grand display of what may be 

 termed an ancient coral reef, formed by zoophytes, 

 which nourished in a sea of earlier date than the 

 carboniferous period. The ledges of horizontal lime 

 stone, over which the water flows, belong to the old 

 red sardstone, or Devonian group, and the softer 

 parts of the stone have decomposed and wasted away, 

 so that the harder calcareous corals stand out in re 

 lief. Many branches of these zoophytes project 

 from their erect stems precisely as if they were 

 living. Among other species I observed large masses, 

 not less than five feet in diameter, of Favosites 

 f/othlandica, with its beautiful honeycomb struc 

 ture well displayed, and, by the side of it, the Favis- 

 tella, combining a similar honeycombed form with 

 the star of the Astrcea. There was also the cup- 

 shaped Cyathophyllum, and the delicate network of 



