258 
GEOLOGY OF THE FOURTH DISTRICT. 
114. 
This structure has been before explained as giving evidence of shallow water, and the 
evidences exist in all the strata of the district which are composed of sand, or sand and clay 
intermixed, from the Medina sandstone upwards. In the purely argillaceous and calcareous 
strata, these markings are not seen. 
In many places the rippled sandstones alternate with shale, presenting a very interesting 
appearance. The edges of the sandstone are undulating, while those of the shale are horizon¬ 
tal, and this is repeated several times in succession. The following section, from the banks 
of the creek above Lodi in Cattaraugus county, illustrates this structure : 
115. 
1, 3, 5. Horizontally stratified shale. 
2, 4, 6. Undulating, arenaceous strata. 
Localities. — There is scarcely a ravine, or bank of a river or stream in the southern range 
of counties, where the rocks of this group are not exposed ; therefore localities for examination 
