334 The American Geologist. 
June. 1903. 
Lorraine stage. 
^Saluda, Madison, or 
Richmond stage J ^^PI^^" Richmond 1,ed, 60 feet. 
1 Middle Richmond, 115 feet. 
[Lower Richmond, 60 feet. 
'Warren bed, 70 feet. 
Mount Auburn bed, 20 feet. 
Corryville bed, 60 feet. 
Bellevue bed, 20 feet. 
Fairniount l)ed, 80 feet. 
Mount Hope bed, 50 feet. 
i Upper Utica, 60 feet. 
Middle Utica, 120 feet. 
Lower Utica, 80 feet. 
The Mount Aubiini Bed. 
The Mount Atibtirn bed is characterized by the presence, 
in great numbers, of a large, globose form of Platystrophia 
lynx,'f with a hinge-line considerably shorter than the width 
of the shell. This globose form may be regarded as a senile, 
gerontic variation of a second, equally large form havino- a 
much greater vertical range. In the second form the hinge 
line ecjuals or slightly exceeds the width of the shell, thus giv- 
ing the shell a more quadrate outline. $ In Ohio, a few stray 
specimens of the large quadrate form are seen in the Fair- 
mount, Bellevue, and Corryville beds ; they occur most abund- 
antly, associated with the gerontic specimens, in the Mount 
Auburn bed ; and they are found in the Morris Hill section, 
three miles northwest of Oregonia, in the Warren bed, forty 
feet above the Mount Auburn bed. In many parts of Ken- 
tucky, especially east of the Cincinnati anticline, the quad "ate 
form has aboitt the same vertical range, namely from the Fair- 
mount to the Warren beds, but it is much more abundant in 
the lower beds there than in Ohio. In Kentucky, therefore, the 
name Platystrophia lynx bed includes a large part of the Lor- 
raine, while in Ohio the name is restricted to the Mount Au- 
burn bed, which is characterized by the presence of numerous 
senile or gerontic specimens. 
In the upper part of the Mount Aubiirn bed at IMadison, 
Indiana, a species of Plectorthis occurs which resembles Plect- 
• Paleozoic seas and barriers, Ui.ivicH and Schuchekt, Report, Kew York 
State Paleontologist, 1901 (Published in 1902), p. 643. 
t "The Morphogenesis of Platvstrophia," H. R. Cumings, Am. four. Sci., 
1903, p 12, 20. 
t Ibid., p. 19, 24. 
