PROGRESSIVE OVERLAP 605 



semireticulatus ; also in the same horizon at White's Creek Springs, and near 

 Colonel Robinson's, on the Middle fork of Cold water, in Lincoln county." 



Spirifer subequalisf Hall. 



Spirif er tenuicostatus Hall? 



Spirifer suborbicularis Hall. 



Spirifer subcuspidatus Hall [Syringothysis texta]. 



Spirifer lineatus Martin. 



Orthis [Rhipidomella] michelini L'Eveille. 



Platyceras equilatera? Hall. 



Oranatocrinus granulatus Roemer. 



Agaricocrmus americanus Roemer. 



Actinocrinus conicos Cassedy and Lyon. 



Actinocrinus nashvillw Troost. 



Actinocrinus (Batocrinus) magnificus Cassedy and Lyon. 



Actinocrinus (Dorycrinus) gouldi Hall. 



Cyathocrinus stellatus Hall. 



Forbesiocrinus meeki Hall. 



Forbesiocrinus saffordi Hall. 



Ichthiocrinis tiarceformis Troost. 



Commenting on these, he says: 



"Most of the above species occurring out of Tennessee are Keokuk forms. 

 Spirifer imbrex and Orthis michelini are found in the Burlington limestone; 

 Spirifer subwqualis and S. tenuicostatus are Warsaw forms, and the latter 

 also Keokuk."* 



The thickness of the Lauderdale in its typical development in Ten- 

 nessee is 250 to 300 feet, but it decreases southward, undoubtedly 

 through the failure of the lower beds. The Tuscumbia, the equivalent 

 of the Saint Louis limestone of Missouri geologists, has a maximum 

 thickness of 250 feet. Safford holds that the lower member (Lauder- 

 dale) thins away southward. He says: 



"In the southern part of the state, at certain points, the member is cherty, 

 crinoidal limestone, resembling the Lithostrotion bed above. In fact, going 

 southward, the lower member becomes thin, and below Huntsville on the 

 anticlinals of Alabama, the two members, in my opinion, become one bed, 

 characterized throughout by Lithostrotion canadense."-\ 



In a foot-note he adds : 



"A little below Gadsden, in Alabama, I have seen a number of specimens of 

 this coral [L. canadense] in an outcrop of the Siliceous chert, very near the 

 Black shale." 



* Ibid. : Loc. cit., p. 343. 

 t Ibid. : Loc. cit., p. 340. 



