274 GENEKAL GEOLOGY. 



On Mosquito creek, Dallas county, layers referable to this 

 bed contain Productus cequico status, Lingula . 



No. 7. Shales, alternating layers of blue, red, yellow, and 

 gray, with irregular nodular bands, and a thin layer of earthy 

 limestone. Seven to thirty feet. At Panora, Guthrie county, 

 a thin band of ash-colored shales in the middle portion of the 

 bed contains great numbers of a minute Aviculoid shell, 



, besides Hemipronites crassus, (?) Productus 



muricatus. Near the top of the bed imperfect remains of 

 plants are not unfrequently met with. 



No. 8. Panora coal. Five to eighteen inches. This bed 

 usually presents a thickness of ten to twelve inches, but 

 locally, in Warren and Lucas counties, it has been found 

 eighteen inches thick. In consequence of the persistent 

 character of this bed, it forms one of the most reliable strati- 

 graphical horizons in the series. The quality of the coal is 

 usually superior to that of the thicker beds ; and, notwith- 

 standing its comparative thinness, it has been mined to a 

 greater extent than any other bed in this formation. Mining 

 this bed is greatly facilitated by the presence of a thin band 

 of limestone, (Bed No. 10), which usually affords a self- 

 supporting roof. Sometimes nodular or flattened masses of 

 pyritiferous shales occur in the coal, charged with Productus 

 muricatus. 



No. 9. Bituminous shales, fissile, and sometimes slightly 

 calcareous. One to three and one-half feet. At numerous 

 localities this bed is richly stored with fossils. Petrodus and 

 spines, Ganoid scales, and undetermined fish remains, 



Aviculopecten rectilateraria, RTiynclionella , Orthoceras 



, Bellerophon carbonaria, Pleurotomaria , Loxo- 



nema , Macrocheilus (?) , Polypliemopsis (?) 



Chonetes mesoloba, Piscina , Atliyris subtilita, Mar- 



tinia planoconvexa, Spiriferina Kentuckensis, , 



, Hemipronites crassus (?) Lingula . 



No. 10. Limestone, impure, dark bluish, weathers brown, 

 and sometimes nodular. This rock is easily disintegrated 

 by exposure to the atmosphere. It varies in thickness from 



