HELDERBERG DIVISION. 
347 
The Pentamerus limestone is a mass of rock some fifty feet in thickness, divided into va¬ 
rious strata and slaty layers, by strata seams, and thin partings of a fine argillaceous slate or 
shale. It contains many genera and species of fossils, and multitudes of individuals of many 
of them. The rock is a slaty and sub crystalline grey and black limestone, containing in some 
places in its upper layers courses and flat nodules of hornstone. It is a very extensive and 
well developed rock in the First geological district, in which it forms a continuous stratum 
from the west line of Schoharie county eastward to the Helderberg mountains in Bern and 
Bethlehem, whence it extends southeast and south to Kingston, and thence southwest by Hur¬ 
ley to Rochester; it then disappears beneath the quaternary of the Mamakating valley, and 
is rarely seen from that place to Carpenter’s point on the Delaware. 
It is well exposed to view near the village of Schoharie, where its fossils have been care¬ 
fully examined by John G. Gebhard junior, esquire, and others, for many years. This gentle¬ 
man has made a more perfect collection of the fossils of this, and of other members of the 
Helderberg division of rocks, than any other person. 
It is well exposed also half a mile south of Sharon springs in Schoharie county ; near the 
Great falls of the Esopus, and in Rochester in Ulster county; and in a great number of 
intermediate places, too numerous to mention. In all the places mentioned, and in a great 
number of others, the base of the Lepocrinites gebhardi is found in abundance in a particular 
stratum, associated with some species of Atrypa and Pentamerus, and the vertebrae of another 
species of encrinite. Plates of the pelvis of the L. gebhardi are also not uncommon. The 
base of the L. gebhardi was first noticed, I believe, by the Messrs. Gebhard, Dr. Foster and 
myself, in 1830; and we called it the Mulberry encrinite, in consequence of a general resem¬ 
blance in form to that of the fruit of the mulberry. 
The above fossil (fig. 5), is characteristic of the middle part of the Pentamerus limestone, 
and has as yet been found in no other position in the First geological district; while the Astro- 
crinites pachydactylus (fig. 6) is equally limited in geological position to the base of this 
limestone, next the upper layers of the Water-limestone group. 
The latter fossil was first found, I believe, by Mr. John S. Bonny, about the year 1829 ; 
and I procured of him, in 1830, specimens more nearly perfect than any that have since 
been procured, with the exception of the specimen represented in fig. 6, This was obtained 
by Mr. B. in 1835, and a slight description was published in one of the Schenectady papers, 
with the above woodcut, under the name of the Actinocrinites polydactylus, which has been 
changed by Mr. Conrad to Astrocrinites pachydactylus. The locality where the specimens 
of this fossil have been obtained most abundantly, is about one-quarter of a mile east of 
Schoharie court-house, at the base of a limestone cliff, at the junction of the dark colored 
limestone of the Water-lime group with the grey pentamerus limestone. The fossils are 
imbedded in a thin stratum of black argillaceous shale, slightly calcareous. The pentamerus 
limestone overhangs the locality, so that it has been only by great labor that the rock could 
be exposed sufficiently to procure even a few specimens. The stems, or vertebral columns, 
are long, and all that I have seen were gracefully curved in arcs of circles or in imperfect 
spirals. 
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