^ K 



356 



On the Silurian Basin of Middle Tefinessee 



howev:er, are not very abiindantj and hence our list is by no 



means as long as the last. 



List of 



1. Stromatoceriun* rugosum, Hall !! 



2. Columnaria aheolata. Hall !! 

 Astrocerium, n. sp. 

 ChfEtetes lycoperdon? Hall. 



" columuaris, ** 



« 1 



3. 

 4. 

 5, 

 6. 



8. 



Strepfela.vna profunda, " 

 Clathropora, sp. undescribed. 

 Stictopora, two new species. 



9. Atrypa recurvirostra, Hall. 



10. LeptiBna filitexta, " 



11. Plearotmnaria rohdoides^ HalL 



12. " subconica, 



13. Murchisonia bicincta, 



14. Actinoceras tenuifilurn, 



15. Orthoceras anellum ? 



16. " multicameratum ? 



« 



« 



« If 



Nashville 



13. This group is not as easily subdivided as the last ; the 

 lowest portion, however, including from sixty to eighty feet, is a 

 well characterized member; the remainderj which is about two 

 hundred and sixty feet thick, not affording grounds for a positive 

 division, has simply been divided equally into Upper and Lower 

 Nashville beds. 



14. (a.) Siliceous or Sandy limestone, — The aspect of this, 

 the first subdivision of the group, is quite different from the 

 purer limestone below ; it is mostly a thick-bedded, coarse-grained, 

 gritty, and, when freshly quarried, dark-bhie, limestone. By 

 weathering it loses its calcareous matter and becomes often a soft 

 yellowish sandstone or shale. 



This member abounds in individuals of Orthis testudinarta, 

 which is highly characteristic, not having been noticed in any 

 other position within the basin. This sub-group, forms a zone 

 enclosing, and concentric with, those described. 



List of Species, 



1. Cheetetes lycoperdon ! 



2. Leptfena, ?p. I 



3. Orthis testudtnaria !!! 



4. Atrypa increbescens. 



5. Spirifer lynx. 



6. Small Aeephal, new !! 



7. Modiolojms anodontoides, 



8. Holopea?! 



Nashville 



Succeeding 



the last, we have thick-bedded strata of bine and blackish-blue 

 limestone running up into thinner layers, separated by seams, and 

 rarely beds of shale. These rocks are generally granular, ofteft 

 gritty and impure, and prone to disintegrate. 



About Nashville, there are two minor beds, which, though of 

 limited extent, are of sufficient interest to be noticed. The first 

 is a bed, at the base of the series, of light clouded blue limestone, 

 from twenty to thirty feet thick, and extensively used for buila- 



mg 



pecul 



surfaces, of finely commimUed fragments of shells, which, to- 

 gether with the oblique lamination observable, proves it to have 



been deposited from a strong current. This is followed by a le^v 





