NIAGARA LIMESTONE. 849 



I,OWER OORAI. BEDS. 



A considerable portion of the transition beds just described are to 

 be regarded as belonging to this division. The rock of this forma- 

 tion is a rough, heavy-bedded dolomite, not unlike the Mayville beds, 

 The layers are sometimes very massive, 12 to 15 feet intervening be- 

 tween distinct bedding joints. In one case, a brecciated reef -like out- 

 lier, 18 feet in height, showed no bedding lines. This massive struc- 

 ture is an occasional feature of this formation. 



In texture, the rock is coarse, crystalline, granular, and usually rath- 

 er soft. Occasional layers are marked by argillaceous seams and par- 

 tings, and by bands or scattered nodules of chert or flint, or by 

 silicified fossils. The softer portions usually contain frequent cavi- 

 ties, doubtless formed by the removal of fossils. These, together 

 with the irregular hardness of the rock, give to the weathered outliers 

 a very rough, craggy, pitted exterior. The prevailing color is gray, 

 verging toward blue, white, and yellow, at times occasionally en- 

 livened by markings of red, pink, and purple. 



Much of the rock is a nearly pure dolomite, admirably adapted to 

 the manufacture of lime. Some portions are, however, quite silicious 

 or argillaceous, and the discrimination recommended in reference to 

 the Mayville beds is to be observed here; indeed, the economic re- 

 marks made with reference to that siibdivision are generally applica- 

 ble here, and need not be repeated. 



Organic Remains. These are abundant and consist very largely of 

 corals, among which the genus Favosites predominates. Brachiopods 

 are next in abundance, among which Fentamerus is most prevalent. 



The following table shows the leading species and local distribution 

 in a compact form : 



