Human Foot-Prints in Solid Limestone, 



19 



There is but one corroborative, though not essential evidence, 

 desirable to add to that ah-eady given in proof of the age of this 

 rock. The uppermost bed of the group to which it belongs is a 

 stratum of limestone of a reddish tint, and characterized by a 

 very remarkable fossil coralline, resembling the Retepora of Z,m., 

 but verticillated spirally like a continuous screw ; described by 

 Lesueur under the appropriate name of Archimedes* Here is a 

 sketch (Fig. 2) of one in my possession : 



Fig. 2. 





Archimedes, of Lesueur. 



In the same rock which contains this fossil, or in the beds im- 

 mediately beneath it, which often exhibit an oolitic structure, the 



* I am not sure that Lesueur ever published his description of this fossil ; but I 

 know that while he resided here (at New Harmony) he engraved a plate contain- 

 ing several views of it, with that intention. He considered it, 1 believe, a new 

 genus ; but it may be only a new species of Retepora; if so, most aptly entitled 

 Retepora Archimedes. 



