204 
GEOLOGY OF THE FOURTH DISTRICT. 
Fig. 1 is a cast in limestone, in which only the concentric lines are visible. In fig. 2, the 
shell is still retained, and presents the two series of lines. This is from the limestone where 
largely intermixed with shale. 
Localities —York; Darien; Alden; Eighteen-mile creek; Seneca lake ; Outlet of Crooked 
lake. 
83. 
The character of the Encrinal limestone of this group is well illustrated in the above wood- 
cut. Fig. 1 is a small portion of the surface of a specimen of this limestone from Eighteen- 
mile creek. From being slightly weathered, the fragments of crinoidal columns, corals and 
shells, stand out in relief. These fragments are sometimes invested with a coral, showing 
that after their destruction they remained long enough upon the bottom for the coral to grow 
and cover them. There are fragments of the columns of several species, of which no perfect 
specimens have ever been found. Fig. 2 is a fragment of a large column, from the shaly 
limestone in Livingston county. The pentapetalous canal has been filled with siliceous matter, 
and the column around has decayed, leaving the former projecting for half an inch. Columns 
of this size and larger are often found, of one or two feet in length ; they are usually furnished 
with branches, and these being broken off, they appear like knotty sticks. 
The following illustration, from the Report of the Third District, presents some of the 
characteristic fossils of this group in that part of the State, where it will be seen from previous 
remarks that the lithological nature of the strata is somewhat different. 
