270 GENEEAL GEOLOGY. 



not received more than a cursory study in that formation. 

 No disturbances, such as faults or dislocations of the strata, 

 have been brought to light in the progress of the examina- 

 tions in this formation, nor is there the slightest indication of 

 such existing. All the irregularites in these strata are such 

 as were produced by irregular deposition and the wave-like 

 undulation mentioned above. 



Fossils. Generally speaking, few species of fossils occur 

 in these beds which can be said to be peculiar to them. 

 Nevertheless, while this formation furnishes a repetition of 

 the organic forms that are found almost throughout the coal- 

 measure series of strata, it is distinguished by certain 

 palseontological and lithological features that furnish infalli- 

 ble guides in the ^identification of its various horizons at 

 localities remote from one another. There is a certain 

 association of forms in the various fossiliferous horizons, 

 such as the prevalence of individuals of one or more species 

 in particular layers, that gives to each of these horizons its 

 prominent distinctive palseontological characteristics. 



Plants. Some of the shales and sandstones have afforded 

 a few imperfectly preserved land plants; three or four species 

 of ferns belonging to the genera, Pecopteris, SpJienopteris, 

 Neuropteris, and grass-like impressions. Besides these, the 

 sandstones contain the remains of Catamites and Sigillaria. 

 The flora, however, is meagre, and does not perform an 

 important part in characterizing any particular horizon. 

 Some of the carbonaceous shales afford beautiful impressions 

 of what appear to have been sea-weeds. 



Of the Peotozoa only the Fusulina has been recognized in 

 these rocks, and this fossil is rare compared with its great 

 abundance in the Upper coal strata. 



Radiates are represented by one or two genera of cyatho- 

 phylloid corals, the remains of Crinoidea and JScMnoidea, 

 and Chcetetes. 



The Mollusks are the most numerously represented of all 

 the other classes of animais. The Polyzoa, BracMopoda, 

 Gasteropoda, and Cephatopods are represented by numerous 



