292 
GEOLOGY OF THE FOURTH DISTRICT. 
4. Cypricardia contracta, n. s. — Oblong, sub-elliptical, very inequilateral; contracted in 
the middle; surface marked by concentric wrinkles, which are stronger toward the anterior 
margin. 
Locality —The three species here figured occur at a single locality about four miles north 
of Panama, Chautauque county. 
Along the northern boundary of Pennsylvania, this conglomerate forms the margin and im¬ 
mediately underlying rock of the coal measures. Tracing it westward into Ohio, we find it 
there holding the same relative position to the rocks of New-York, and to the coal, that has 
before been shown. The absence of the Old Red sandstone brings it directly in contact with 
the Chemung group below, over all the western part of New-York, and it holds the same place 
in Ohio at all localities examined. As before remarked in the last chapter, the intervening 
strata which separate this rock from the Chemung group are absent, having apparently never 
been deposited over a very large tract of country. Its outliers in the Fourth District offer 
less satisfactory sections than the same rock when more continuous. 
The following section at Cuyahoga falls, in Ohio, exhibits the relative position of this rock 
and its associates. 
140 . 
The river bank presents the two lower rocks in connection, and the coal beds with shales 
and sandstones occupy a slope extending eastward from this point. This is near the western 
extremity of the coal-field; and when we next meet the conglomerate in a western direction, 
we find it resting upon a limestone, and its relation to the rocks of New-York is illustrated 
in woodcut No. 129 on page 280. 
The conglomerate still holds its relations to the coal measures as before, forming the 
eastern and southern margin or edge of the Great coal-field of Illinois and Indiana, which 
likewise extends into Kentucky. The same rock forms the western margin of the Ohio coal 
measures throughout the State, and extends north and eastward, as just mentioned, bordering 
the Pennsylvania coal-fields ; and Prof. Rogers remarks, that it also extends into Maryland 
and Virginia, holding the same relative position. These facts are of the highest interest, both 
in an economic and scientific view ; for since its extent is so well marked and widely known, 
it may, in all places, be relied upon as indicating the proximity of coal. 
