100 The American Geologist. August, 1904. 
Ohio, and another in. the Whitewater bed at Tate hill, east of 
Dayton, Ohio. Strophouicna sulcata occurs in all subdivisions 
of the Richmond, but it is common only in the upper part of 
the Waynesville bed and, again, in the upper part of the 
Whitewater. 
7. Dinorthis retrorsa. 
Dinorthis retrorsa has been considered hitherto one of the 
most characteristic fossils of the Warren bed. It is found in 
the Warren bed at numerous localities in southern Indiana, 
although restricted to a vertical range of only a few inches 
near the middle of the bed. At Madison, it occurs 47 feet 
below the top of the Warren ; east of Cold Springs station on 
the Baltimore and Ohio Southwestern it is 32 feet below ; east 
of New Trenton the species ranges from 33 to 35 feet below ; 
half a mile above the mouth of Pipe creek it occurs at least 35 
feet below. 
Recently a variety of Dinorthis retrorsa has been found 
also in the upper part of the Waynesville bed, about 25 to 30 
feet below the top. It occurs 30 feet below the base of the 
Hehertella insculpta layer, directly in front of the home of 
Nick Senefeld four miles southwest of Brookville, immed- 
iately overlying beds containing Bythopora meeki, Eridotrypa 
simulatrix, Heterotrypa prolifica, Homotrypa flahellaris, and 
Nicholsonella tenera. Dinorthis retrorsa was found loose 25 
feet below the top of the Waynesville bed at the home of Wil- 
liam Bauman, three miles southwest of Brookville. About 
half a mile above the mouth of Silver creek, opposite the home 
of Robert Martin, it occurs 47 feet above the creek and 17 feet 
below the top of the exposure, all of Waynesville age. Here 
Bythopora meeki, Callopora subnodsa, Hetrotrypa prolifica, 
Monotrypella qnadrata, Nicholsonella tenera, and Spatiopora 
inontifera were found immediately below this upper Dinorthis 
retrorsa horizon. The top of the Waynesville bed was not 
exposed. At all Waynesville localities specimens are rare ; the 
valves are usually separated ; they differ from the Warren bed 
forms in the smaller number and greater width of the radiating 
plications. The Warren form was described by Hall as Dinor- 
this carleyi; a more careful discrimination between Ordovician 
faunas will probably lead to the revival of Hall's name for the 
Warren form. 
