16 



character.* Similar spores occur in vast numbers in Devo- 

 nian shales and limestones of various parts of the United 

 States and Canada, and to them the name Sporangites 

 (Protosalvinia) huronensis was given by Dawson. Allied 

 spores have been discovered in widely separated localities all 

 over the world, and they are not infrequently found in such 

 quantities as to suggest that they may play a not unim- 

 portant role in the accumulation of vegetable carbon. In 

 the Devonian shales of this country they probably constitute 

 one of the sources of petroleum and natural gas. Spores are 

 occasionally found in the gray portion of the shale, but they 

 are very rare. 



The spores are, as a rule, readily separated from the shale, and may 

 be mounted either in balsam or dry. When viewed under the micro- 

 scope by transmitted light, the discs appear of an amber or orange hue, 

 translucent and structureless, except for minute spots, which are 

 regarded as pores in the thick walls. The size varies ; the ordinary 

 specimens having a diameter of from one seventy-fifths to one one- 

 hundreds of an inch (one-third to one-fourth of a millimeter). Some of 

 the spores, however, are larger. Flocculent carbonaceous matter often 

 occurs, associated with these macropores, probably representing the 

 more or less decomposed microspores. 



These shales mark the base of the Genesee stage, and, since 

 theTully limestone is absent, the base of the Upper Devonian. 



The Moscow Shales. These, the upper shales of the Middle 

 Devonian, are exposed near the lower end of Section 1, where 

 about a foot is visible. The top of the series is formed by a 

 gray concretionary limestone band, four inches thick and 

 highly argillaceous. It is a very refractory rock, and of a 

 uniform texture throughout. Fossils are common, but they 

 are chiefly of three species which characterize this horizon. 

 These are : 



Liorhvnehus multicostus (Hall). 

 Schizobolus truncatus (Hall). 

 . 1 mbocoelia praeumbona ( Hall ). 



'According to New lurry, the carbonaceous matter of the bituminous shales is 

 mainly derived from the broken down and carbonized tissues of algae and other 

 low plants. See his paper on this subject in the Annals of the New York Academy 

 "I Sciences, Vol. 11., No. 12, 1NS3. 



