Variations of the Ordovician of Indiana. — Focrstc. loi 
8. Leptaena rhomhoidalis. 
Lcptaena rhomhoidalis ranges in the Warren bed of War- 
ren county, Ohio, from three to four feet beneath the Din- 
orthis rctrorsa horizon to a short distance above this horizon. 
It occurs at the same horizon in Indiana, on Big- Cedar creek 
in Frankhn county and a mile southeast of Sparta. However, 
it is abundant and widely distributed only in the upper third of 
the Waynesville bed. At the Bauman locality, three miles 
southw^est of Brookville, it makes its appearance at the upper 
Dmorthis rctrorsa horizon, becomes abundant lo feet higher, 
and extends through the Hehertclla insculpta layer. It makes 
its appearance at the upper D. rctrorsa horizon also along Sil- 
ver creek, half a mile east of Dunlapsville. A mile and a half 
west of Blue creek postofifice, east of the creek, it is found in 
the Hebcrtclla insculpta layer. South of St. Leon it is abund- 
ant for five feet above the Hehertclla insculpta layer, immed- 
iately below the Plectamhonitcs sericeus horizon. Occasionally 
specimens are found at the top of the \\niitewater bed at Rich- 
mond. 
p. Rhynchotrcina dentation, Rh. capax. 
Another fossil showing recurrence at dififerent elevations is 
Rhynchotrema dentatnui. A variety wnth fewer and more 
angular plications occurs in the Warren bed, 22, feet below the 
lowest strata definitely recognized as Richmond, half a mile 
southwest of Howard Mill, in Kentucky. The typical form oc- 
curs near the top of the Waynesville bed at Versailles and at 
Metamora. It is rather common in the upper Whitewater beds 
at Richmond and east of Dayton, Ohio. Rhynchotrema capa.x 
occurs at Madison seven feet above the massive coral layer at 
the base of the Madison bed. It occurs much more abundani 
ly in the other subdivisions of the Richmond. 
10. Plectambcnites sericeus. 
Plectamhonitcs sericeus occurs occasionally near the base 
of the Waynesville bed west of Oxford, Ohio. It is abundant 
a short distance above the Hebcrtclla insculpta layer in the 
Liberty bed. 
11. Platystrophia lynx. 
In southern Indiana, and in the adjacent parts of Ken- 
tucky, Platystrophia lynx is very abundant in the Bellevue 
bed. In Ohio, it occurs occasionallv in the Fairmount, Belle- 
