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AN OLp SHORELINE. By D. W. DENNIs. 
The Elkhorn is a small tributary to the Whitewater River from the 
east, some four miles south of Richmond, Ind. There is in this stream a 
falls some twenty feet in height that has receded and left a gorge of 
about that depth for a distance of a half mile or more; this gorge is cut 
through strata of the same age as those through which the Niagara gorge 
passes. At the Elkhorn the surface rock is the Niagara limestone; it is 
massive and some twelve feet thick; it is underlaid by the uppermost 
layers of the Lower Silurian formation, consisting of alternating layers 
of thin flagstones and clay. This clay and fragile flags wear faster than 
the overlying massive rock, and so it shelves over; one can pass behind 
and around the falls just as he can parts of the Niagara Falls. The fos- 
sils in the Lower Silurian strata are the same one finds in the gorge at 
Richmond. In the uppermost stratum, however, they are beach-worn, 
ground in many instances to unrecognizable fragments; a half dozen spe- 
cies can, however, be made out—enough to settle the question of its age 
without dispute; it is Lower Silurian; it is an ancient coquina rock; it 
crops out for a distance of half a mile; tons of it can be examined; its 
story is as interesting as it is unmistakable; here was the beach of the 
Cincinnati Silurian Island; the wearing of the stones has not been in 
recent geological times, for they are restratified and are overlaid by the 
Niagara rock, which bears glacial striz on its surface. After these rocks 
were beach-worn, the sea deepened, the shore line moved eastward and 
remained there long enough for the twelve feet of Niagara rock to form 
in a clear—clayless—sea. 
Two CASES OF VARIATION OF SPECIES WitH Horizon. By D. W. Dennis. 
The east fork of the Whitewater River has worn a gorge in the upper 
strata of the Lower Silurian limestone, near Richmond, Ind. This gorge 
is about 75 feet deep, is terminated by a falls a half mile above the city, 
and for a distance of some two miles below the falls the river bluffs are 
generally precipitous. This Lower Silurian formation consists of flag- 
stones four inches or less in thickness, alternating with clay strata of 
about the same thickness. The flags are made up chiefly of the shells 
