J^ariations of the Ordovician of Indiana. — Foerstc. 91 
ning southward of the upper beds of the Lorraine, but suggests 
very Httle change in the thickness of the Bellevue-Fairmounc 
section between Madison and Fredericktown. In south-central 
Tennessee, the Lorraine section. 100 feet thick, inckides thv=r 
Fairmount, Bellevue, and Corryville beds ; with Platystrcphin 
lynx in the uppermost beds. 
4. Diminution in Thickness of tJie Subdivisions of the 
Richmond. 
While there is no doubt of the considerable diminution in 
thickness of the Richmond group as a whole, from the more 
northern outcrops in Ohio and Indiana southward, the relative 
diminution of its different subdivisions can not be determined 
definitely until their characteristic faunas are better known. 
However, in the mean time, a number of very suggestive ob- 
servations, connected with the interval between the base of the 
HcbcrtcUa insculpta layer and the base of the Waynesville bed, 
also %vith the interval between the base of the H. insculpta lay- 
er and the base of the beds at present referred to the Madison, 
will prove of interest, especially in view of the fact that the 
base of the Herbertella insculpta layer has been proposed as 
the base of the Liberty division of the Middle Richmond. 
a. Intervals betzveen HebertcUa insculpta layer, base of 
Waynesville and top of Whitczvatcr beds north of Madison. 
Comparatively little variation is noticed in the vertical di- 
mensions of the interval between the base of the HebertcUa in- 
sculpta layer and the base of the Waynesville bed between Un- 
ion county, Indiana, and Madison. This interval amounts to 
about 83 feet at the localities west of the home of ^^''illiam 
Bauman on McCarthy creek southwest of Brookville; about a 
third of a mile above the mouth of Pipe creek ; southeast of 
Cedar Grove on the road to South Gate ; and north of Hogan 
creek on the road from Moores Hill to Holman. Along Silver 
creek in L'nion county the interval is probably equally great, 
smce the exposures of the Waynesville bed opposite the home 
of Robert Martin equal 64 feet without exposing either the 
HebertcUa insculpta zone or the base of the Waynesville bed. 
Southwest of Friendship on the road crossing the southeastern 
corner of section 13, also two miles southeast of Belleview on 
a road crossing Indiankentuck river, this interval is 70 feet. 
Southeast of Belleview, the thickness of the Richmond is 166 
