OF ARKANSAS. 12] 
escarpment on the north bank of the Barren fork, extending down to the 
bed of that stream. 
The different beds and their order of superposition, from the schistose 
sandstone of College hill, to the cherty limestone of the Barren fork of the 
Illinois river, are shown in the annexed section. 
A modification is ob- 
servable in this section, 
causing it to differ from 
Feet. 
Inches. 
Schistose sandstones of College hill. those sections previously 
4 
wea ; given of the strata under 
L | oL the Archimedes lime- 
| L | 5 ee limestone over the Boonsboro BHOne : it consists in the 
introduction of the build- 
ing-stone amongst the 
underlying shales. Near 
_ the Barren fork, the 
===] 152 Dark shales, 10 to 15 aeelan thickness. strata have a strong dip, 
—- 9 to 18 deg. north north- 
east and north-east. 
4 Freestone or building-stone. 
| a , 
; The fossiliferous lime- 
— — stone lies in a pavement 
2 p : 
———| iiss form, with a regular and 
oe pete — deeply marked system of 
LLLE Fossiliferous limestone. j oints, havin g a course 
ons SHaseHne: north-west and _ south- 
req east. The most abund- 
GE hae ant fossils in this rock are 
x | 40 |- | Ghert and cherty limestones of the Barren Poach 1 1 ee 
[cu |} fork of the Illinois. River. erebratula plano-sulcata 
cu | cu and planum-bona; Pro- 
| cu | ductus cora and a Pro- 
cL | cL 
ductus allied to P. semi- 
reticulatus ; a favosite re- 
sembling the basaltica, but so deeply imbedded and firmly attached in the 
substance of the rock that they could not be properly examined in place, 
nor detached without defacing them in such a manner that the disposition 
of the rows of connecting pores could not be seen so as to determine their 
specific character. _— 
Both Productus cora and Terebratula plano-sulcata were found, also, in 
the overlying chert. 
This limestone has marly and shaly partings. 
‘Black shale ? 
