Association of American Geologists and Naturalists. 161 
poraneous with the New Red, and were doubtless deposited during 
the long period that marked the upheaval of the trap, as trap 
was found, in a very coarse condition, to enter largely into the 
fragmentary material, composing, more particularly, the lower 
strata of these rocks. 
Dr. H. proceeded to state, that the Pentremite limestone men- 
tioned by Mr. Owen, in the part of his paper read yesterday, 
seemed gradually to thin out as it went north, and to exist, after 
we lose it in continuous beds, in strips and patches. 
Prof. H. D. Rogers then said, that if he understood Mr. Hall, 
he considered the black bituminous slate of the west, as the 
equivalent of the Marcellus shale and Hamilton group of the 
New York system combined. A careful examination of that well 
characterized stratum had led him and his brother, Prof. W. B. Ro- 
gers, to regard it rather as the representative of the Marcellus shale 
alone. ‘They had during the last summer and autumn traced 
both the Marcellus shale and the Hamilton through Pennsylvania 
and Virginia and East Tennessee, to their southwestern termina- 
tions, the former thinning out in Virginia, and the latter abruptly 
disappearing with the ending of the Clinch Mountain in an enor- 
mous fault in East Tennessee. The Marcellus shale, unaccom- 
panied by any indications of the Hamilton group, was subse- 
quently identified by its fossils during the same tour by Prof. 
Hi. D. Rogers, at Canary Fork, the Harpeth Hills near Nash- 
ville, and other localities in Middle Tennessee ; also in Kentucky, 
southwest of Louisville, and at New Albany in Indiana, the fos- 
sils most frequently met with being the Orbicula corrugata, and 
aminute Lingula. Prof. R. thought that the Hamilton group— 
of which he could discover no trace by organic remains in the 
west, being in New York so remarkably replete in fossils—would 
in accordance with a general law of our strata continue some, at 
least, if not many of its species, as far westward as its sediment- 
ary materials. 
He next adverted to his having met with what he considered 
the Dictuolites Beckit, a Medina species, and F'ucoides biloba, a 
Clinton form, in the so-called blue limestone formation of Cincin- 
nati, and the Strophomena rugosa of the Clinton and higher 
groups of New York in the same blue limestone at Madison, In- 
diana. . 
Vol. xiv, No. 1.—April-June, 1843. 21 
