248 The American Geologist. 
October, 1905 
Arnheim bed is of interest, is Dalmanella jugosa. This 
species occurs in such great numbers in the lower part of 
the Waynesville bed in most parts of Ohio and Indiana, 
that this part has been called the Dalmanella zone. How- 
ever, it occurs at some localities also in considerable num- 
bers in the middle and lower part of the Arnheim bed. 
This is true especially in Franklin county, Indiana. Its 
range begins at least 10 or 15 feet below the Dinorthis re- 
trorsa zone, and extends for several feet above the latter. 
On the eastern side of the Cincinnati geanticline, at Arn- 
heim, Ohio, Dalmanella jugosa is rather abundant in a layer, 
nine inches thick, also containing Platystrophia lynx which 
is nearly 9 feet below the Dinorthis rctrorsa horizon. It 
occurs associated with Platystrophia lynx, also at Mays- 
ville, Kentucky, eight feet and three inches below the low- 
est specimens of Leptaeria rhomboidalis and a greater dis- 
tance below the Dinorthis rctrorsa horizon. At most 
localities, however, Dalmanella jugosa rare, or even ab- 
sent, in the Arnheim bed. 
Dalmanella jugosa is found associated with Dinorthis 
retrorsa, Rhynchotrema dent at a, and Leptaena rhomboid- 
alis at Clifton, Tennessee, and is associated with Platy- 
strophia lynx, and Rhynchotrema dentata at Xewsom, in 
that state. 
On going from Mavsville, Kentucky, and Madison, In- 
diana, southward, toward central Kentucky, the lower part 
of the Richmond is found to become rapidly more argilla- 
ceous and less fossiliferous. At the more southern locali- 
ties, in central Kentucky, there are no specimens of Strepte- 
lasma, Protarea, Sttophomena, Leptaena, Rhynchotrema 
capax, no numerous specimens of Dalmanella jugosa pres- 
ent, as in the lower part of the Richmond in ( )hio and most 
of Indiana. A thin zone of bryozoans, several feet thick, 
is found at the very base of the Richmond, but, for those 
who do not make a special study of bryozoans, their identi- 
fication is not easy, and their utilization for determining the 
boundaries between the Richmond and Mavsville or Lor- 
raine divisions of the Cincinnatian becomes impracticable. 
Hence the great value of the Dinorthis retrorsa, Leptaena 
rhomboidalis, Rhynchotrema dentata horizon for the aver- 
