204 The American Geologist. 
October, 1903 
those formed in the western and northwestern parts of the ancient inter- 
ior sea, now exposed at Wilmington and Sterling, Illinois, and Spring 
Valley, Minnesota, perhaps also those shown at Dalaneld and Iron 
Ridge, Wisconsin, all of which have been referred to the Cincinnati 
period, may represent a phase later than any of the Richmond of Ohio 
and Indiana. 
"The Richmond group has a very extensive and varied fauna, and 
as a whole, very different from the underlying Lorraine. Corals are 
unknown in the Lorraine, the Richmond has a considerable number. The 
bryozoan fauna of both lower and middle Richmond is very extensive; 
many new species of Bryozoa have been discovered which await de- 
scription." 
In another part of the same paper (p. 64) the thickness of 
the Richmond is stated to be "between 200 and 300 feet." 
Field work in Ohio and Indiana by the writer during the 
summer of 1902 at points noted for their exposures of Rich- 
mond strata, has shown that both the earlier and later charac- 
terizations, so far at least as Ohio and Indiana are concerned, 
are inaccurate and even erroneous in some points. Winchell 
and Ulrich give the thickness as 350 feet. This is too great. 
As they did not give the boundaries between the Utica, Lor- 
raine and Richmond, when characterizing these formations.* 
they have probably included in their Richmond the Warren 
beds, typically shown about Lebanon, Ohio, which the writer 
considers of Lorraine age.f It is not easy to determine the 
thickness of the Richmond. It probably varies somewhat in 
different parts of the area, local conditions having influenced 
the amount of sediment deposited. It is also possible that some 
of the upper beds were eroded away in places, before the over- 
lying Clinton was deposited. The average thickness lies be- 
tween 160 and 200 feet. No place is known to the writer where 
all the beds are exposed so that a complete section can be meas- 
ured. 
It has also been seen that the Richmond has four well marked 
subdivisions. The lowest and the greater part of the highest are 
not shown at Richmond, Indiana. The only point known to the 
writer where all the divisions appear, and no other formations 
than those of the Richmond, is Versailles. Hence this would 
have been a better locality than Richmond from which to select 
the name for the group. 
* Geology of Minnesota, iii, Part 2, p. cii. 
t Jour, Cincinnati Hoc. Nat. Hist., xx, No. 2, p. 75. 
