ISOTELUS, ACROLICHAS, CALYMENE, AND ENCRINURUS 67 
tion. The trilobite was lying on its back, and it remained 
attached to the upper half of the indurated clay layer in which 
it was imbedded. Five feet above the trilobite horizon was 
found a single specimen of Columnaria vacua Foerste. Since in 
the northwestern quarter of the Waynesville quadrangle the 
Hehertella insculpta layer, forming the base of the Liberty meni- 
ber of the Richmond formation, lies about 165 feet beneath the 
base of the Brassfield formation, the horizon at which the large 
Isotelus at the Huffman Conservancy dam was found must be 
either in the base of the Liberty member or near the top of the 
Wajmesville member of the Richmond formation. The writer is 
indebted to Arthur E. Morgan, chief engineer of the Miami 
Conservancy District, for the privilege of studying this specimen. 
At the bluff adjoining the southern end of the Huffman Con- 
servancy dam the Brassfield limestone is underlain by the Elk- 
horn clay shale, 60 feet thick, and this in turn by the White- 
water member of the Richmond, but the line of contact of the 
Whitewater with the Elkhorn could not be determined on ac- 
count of the muddy clay adhering to the rock as the result of 
continuous quarrying operations. 
A second large specimen of Isotelus, apparently belonging to 
the same species as the Huffman Conservancy dam specimen 
was found by Dr. George M. Austin in the Isotelus clay layer in 
the upper or Blanchester division of the Waynesville member of 
the Richmond formation, at a locality about 2^ miles northeast 
of Oregonia, in Warren County, Ohio. This locality is on 
Roaring Run, about three-quarters of a mile northwest of the 
Flat Fork school. The length of this specimen was 23.5 cm. 
The original was an impression in clay, the trilobite lying on its 
back, and of this impression Dr. Austin secured the plaster of 
Paris cast, here illustrated on plate XV. In all essentials this 
smaller specimen is similar to the larger specimen, described 
above. The ratio of the length of the head to its width is as 
five to ten. The ratio of the length of the pygidium to its width 
is 58 per cent. The basal part of the genal spine on the right 
side of the specimen is preserved, but its tip is gone, so that 
there is no means of determining its exact length. It probably 
