14 GEOLOGICAL STRUCTURE OF THE 



spots behind the eyes ; eyes black ; spring flesh- 

 coloured. 



Length rather more than one- twentieth of an inch. 



Cabinet of the Academy. 



Found under the bark of the long leaved Pine, 

 (P. palustris) in Georgia. 



Observations on the Geological Structure of the Val- 

 ley of the Mississippi. By Thomas Nuttall. 

 Read, December 1820. 



§ I. the probable limits and character of the 



SECONDARY FORMATION. 



The near approach which the calcareous and other 

 strata west of the Alleghany mountains make to the 

 horizontal line, considering their inherent character, 

 ha* been a matter of surprise to those who are any 

 way familiar with the geology of Europe. A number 

 of hand specimens, which some years ago I compa- 

 red with what is called the compact mountain lime- 

 stone of Derbyshire, in England, presented not a 

 single dissimilar feature, either in regard to compo- 

 sition or organic reliquiae ; and I am fully satisfied, 

 that almost every fossil and shell figured and descri- 

 bed in the " Petrificata Derbiensia" of jVJartyn are 

 to be met with throughout the great calcareous plat- 

 form of the Mississippi valley. We everywhere, 

 perceive the same host of Terebratulites, Alcyo- 

 oites, and Encrinal vertebrae ; the same zoophi- 



