CARBONIFEROUS SYSTEM. 281 



horizon of the "upper division. Its organic remains, so far as 

 known, consist of the following species : Petrodus and spines, 



Beyrichia Americana, Aviculopecten rectilateraria, Discina 



Lingula , and beautiful fucoidal impressions. 



No. 38. Limestone, dark and grayish blue, fragmentary 

 and sometimes nodular, impure; six inches to two feet. This 

 rock rarely answers for building purposes ; besides, it is 

 seldom of sufficient thickness to quarry to advantage. It 

 furnishes, however, a reliable horizon, and it derives much 

 interest on account of the prevalence of certain species of 

 fossils which are of comparatively rare occurrence in the lower 

 beds of the formation and which give to this horizon a 

 somewhat striking palseontological resemblance to some of 

 the beds in the Upper coal-measures, as is exhibited in the 

 accompanying list of the forms common to this bed: Fusulina 



cylindrica, rare, Zaphrentis , crinoidal remains, Polyzoa, 



two or three species, Spirifer cameratus, common, Spiriferina 

 Kentuckensis, Martinia lineatus, common, M. planoconvexa, 

 common, Athyris subtilita, Retzia punctdifera, Productus longis- 

 pinus, common, P. punctatus, (?) P. aequicostatus, P. Nebracensis, 

 P. muricatus, Chonetes mesoloba, always very small, C mucronata, 

 C. Verneuilianus, Hemipronites crassus, (?) Aviculopecten rectila- 



teraria, Pernopecten , Allorisma , Bellerophon 



crassus, (?) Phillipsia . 



No. 39. Light, red and blue shales, with arenaceous 

 layers ; twenty to forty -five feet. At the base of the stratum 

 locally developed fossiliferous shales afford the following 

 species: Cyathaxonia , (sp. ?) crinoidal remains, Produc- 

 tus punctatus, P. longispinus, Chonetes m,ucronata, Hemipronites 

 crassus (?), Spiriferina Kentuckensis, Martinia planoccnvexa, 



Athyris subtilita, Retzia punctilifera, P leurotomaria , 



Bellerophon carbonarius, B . 



No. 40. Eather compact, thin bedded, buff limestone; 



fiYQ to ten feet. This bed is sometimes locally represented by 



compact heavy bedded layers, and sometimes accompanied 



by thin bands of limestone inter stratified with shales. It 



burns into dark colored very strong quicklime, and is a 

 36 



