The Cinciniiatian Scries and its' Brachiopods. H 



Mud-balls. — In some limestone layers there are rounded 

 masses of shaly material, varying in size from one to three 

 inches in diameter. The material is very different from that 

 of the containing stratum, being best shown when in lime- 

 stone made up of comminuted shells. Upon weathering 

 these masses are in some cases released from the containing 

 limestone and may be found free on the surface. These 

 masses are interpreted as fossil mud-balls. They were 

 probably formed from irregular masses of mud broken off 

 by waves from mud layers nearby or just beneath the newly 

 forming sediments. After being worn and rounded by the 

 waves the mud-balls were dropped and became imbedded 

 in the finer sediment being deposited. 



Sun-cracks.- — Sun-cracks are not known to exist in the 

 Eden or Maysville formations, but are quite prominent in 

 some of the shale layers of the Saluda member of the Rich- 

 mond. They indicate extremely shallow water conditions, 

 with short emergences, allowing the mud to dry partially 

 and crack, before being covered with another layer of sedi- 

 ment. 



Worm borings. — Many of the more shaly strata are 

 curiously marked with what are thought to be worm borings. 

 These worm borings are of two types: — (1) those extending 

 along the bedding planes, and (2) those passing into and 

 through the beds. The first type probably represents the 

 path of worms crawling along the sea-bottom; the second, 

 of worms burrowing into the mud. 



2. Secondary. — Under this class of structural features 

 are those indicating subsequent events. They include the 

 Cincinnati anticline, local folds and faults, and joint cracks. 



The Cincinnati anticline. — The strata of the Cincin- 

 natian series at Cincinnati appear to be horizontal. They 

 are, however, part of a low broad anticline extending from 

 Nashville, Tenn., northward through Kentucky, to Cin- 

 cinnati. Near Cincinnati the anticline divides into two 

 branches, the one extending northwestward toward Chicago, 

 the other northward through western Ohio. This anticline 



