354 The American Geologist. ''^'"'- ^'''^• 
considered characteristic of the Richmond stage. As a rule 
the lowest strata containing characteristic Richmond 1)rachio- 
pods or the coral bed immediately beneath, wherever anv coral 
bed occupied this position, was regarded as forming the base 
of the Richmond section. Much new light will undoubtedly 
be shed upon this question when the bryozoams, the most valu- 
able horizon markers of the Ordovician, are more fullv studied. 
The Upper Richmond. 
At Madison, Indiana, the greater part of the Upper Rich- 
mond consists of the nearly unfossiliferous, massive, banded, 
argillaceous limestone which forms a conspicuous element at 
all waterfalls and other steep cuts near the upper part of the 
hills. This rock can be distinguished readily from any other 
rock in the section.. Southward it can be traced with ease as 
far as Charlestown Landing in Clark county in Indiana. Typ- 
ical exposures occur at numerous localities in Oldham, Jeffer- 
son, and BuUit counties, in Kentucky. The exposures of the 
massive limestone at the top of the Ordovician section south of 
Mount Washington, and at the Asa Lutes and Kirby Jones lo- 
calities are lithologically identical with those along the Ohio 
river in the southern part of Indiana. Similar rock is also found 
south of the Kirby Jones locality, in Nelson and Marion coon- 
ties, Kentucky. Here, however, the thickness of the Upper 
Richmond section is much less, and the massive rock forms a 
less conspicuous part of the section. It has not yet been defin- 
itely demonstrated that the richly fossiliferous beds above the 
Bardstown coral reef in Nelson and Marion tounties belong 
to the Middle and not to the LIpper Richmond. At present, 
however, they are regarded as of Middle Richmond age, and 
the base of the immediately overlying, nearly unfossiliferous 
portion is regarded as the base of the upper Richmond. 
C. Conclusions. 
The following conclusions are offered as perhaps the most 
reasonable in the present condition of our knowledge. 
The Lower Richmond diminishes in thickness from Fort 
Recovery in western Ohio, southward. West of the Cincin- 
nati uplift, the last traces of the Dalmaiiclla jiigosa zone are 
seen at Marble Hill in southern Indiana. The upper part of 
the Lower Richmond can be readily identified cit the moutli of 
Bull creek ; it is probably present at Mount Washington and 
