Distribution of Brachiopoda, — Foerste. 249 
age investigator. With this horizon as a guide, the line be- 
tween the Richmond and Maysville, determined at a few 
localities by an expert on bryozoans, may be followed for 
long distances merely by taking advantage of lithological 
differences. 
Another point of interest in connection with this Dinor- 
tliis retrorsa, Rhynchotrema dentata, and Leptaena rhom- 
boidalis zone at the middle of the Arnheim bed is their re- 
currence in the Waynesville bed. They are found in the 
upper third of the Waynesville bed in various parts of 
Union and Franklin counties, Indiana ; and RJiyncliotrema 
dentata and Leptaena rhomboidalis, without the presence 
of Ditwrthis retrorsa, are widely distributed at this horizon 
in Ohio. Indiana, and adjacent Kentucky. 
A most interesting case of the recurrence of species has 
recently been discovered by Dr. George M. Austin at Stony 
Hollow, ,north of Todd fork, at Clarksville, southwest of 
Wilmington, Ohio. Here Herbertella insculpta occurs in the 
Waynesville bed thirty feet below the chief Herbertella in- 
sculpta horizon which is used to distinguish the Waynes- 
ville bed from the Versailles or Middle Richmond bed. 
Zygospira kentnekiensis was found 15 feet below the top 
of the Waynesville bed, and about 45 feet above the base. 
East of Pendleton, Kentucky, Zygospira kentnekiensis oc- . 
curs in association with Tetradium fibratum and Calopoccia 
cribrifor/tns, 5 feet below r the lowest layers containing 
Streptelasma rusticum and t Strophomena planumbona, and 
between 40 and 50 feet above the base of the comparative- 
ly nonfossiliferous beds which here represent the middle and 
lower part of the Waynesville bed. The same Zygospira 
kentnekiensis horizon is exposed at the mouth of Bull Creek 
Clark county, Indiana. Here the lowest layers containing 
Dinoi tliis subquadrata occur 20 feet above the top of the 
Zygospira kentnekiensis horizon, with Streptelasma rusticum 
Columnaria //alii, Strophomena planumbona and Rhyncho- 
trema capax in the intervening rocks. This Zygospira ken- 
tnekiensis horizon, with the overlying fossiliferous beds may 
be traced as far southward as Lebanon, Kentucky. It was 
noticed by Linney in Nelson county, Kentucky (Geology of 
Nelson county, 1884, page 34). The Rhynchottema denta- 
