222 GEOLOaY OP ohio. 



follows a tortuous course through sections 35, 36, 37, 25, 20, 21, and 27, 

 into sections 28 and 35 of Londonderry. In this latter section the direc- 

 tion, previously north-west, is changed to south-east, through 35, 29, and 

 22, into 15, 8, and 2 of Oxford, where the course becomes north-east 

 through 3 of Oxford into 4 and 5 of Londonderry, from which it crosses 

 into 36 of Kirkwood township, Belmont county. Isolated patches are 

 found on the western side of the anticlinal in sections 20 and 25 of Lon- 

 donderry, 13 and 17 of Madison, and very probably in 10 and 17 of Jeffer- 

 son, though in this latter case the coal was not observed. In Guernsey 

 county the roof of Coal No. 8 is usually sandstone, sometimes separated 

 by a few inches of shale, and the roof-coal is rarely present. Sandstone 

 "horsebacks," of considerable extent, and "clay veins" are of frequent 

 occurrence, and have a direction rudely north-east and south-west. The 

 thickness of the coal varies little from four feet, and the quality is infe- 

 rior to that of coal brought from the river. The strata below this eoal to 

 a depth of about one hundred and fifty feet are subject to great and sudden 

 variations, sometimes consisting almost entirely of sandstone, while at 

 others they are almost wholly shales. 



The Crinoidal limestone, though thin, is an exceedingly important 

 stratum. In the Barren Group, where the coals vary abruptly and the 

 accompanying strata are for the most part characterless shales and sand- 

 stones, the geologist would be frequently at a loss unless some well-char- 

 acterized stratum were found marking a definite horizon. Such a guide 

 is found in this little limestone, which lies almost midway between Coals 

 Nos. 7 and 8, being ordinarily one hundred and fifty feet above the former 

 and one hundred and fifty to one hundred and sixty feet below the lat- 

 ter. It is usually very hard and impure, weathering into blocks dull 

 gray outside, and dingy brown, or light gray, on the freshly fractured sur- 

 face. The weathered exterior is covered with plates and spines of cri- 

 noids, together with many spines of moUusca. The specimens frequently 

 weather entirely free from the rock, and several species common through- 

 out the Ohio Coal Measures can be obtained in good condition from this 

 stratum alone. Fossils can be collected at Quaker City, at Salesville, at 

 several points along the road from Salesville to Washington, as well as 

 between Birmingham and Londonderry. The rock is well exposed in 

 Millwood, Wills, Center, Knox, Madison, Washington, and Londonderry 

 townships. The following is a list of its fossils : 



1. Crinoidal plates. 



• 2. Crinoidal columns. 



.i. Zeacrinus mucrospinns M'C. 



4. Lophophyllum proliferum M'C, Sp. 



