1^0. .50] 
237 
jr. of Schoharie, who was the assistant for Schoharie county, has exa=' 
mined this group with much attention for several years, and he has a 
more perfect collection of the fossil remains of its various strata than 
any other individual. 
The Helderberg series is a part of Prof. Rogers' olive slate group," 
or formation No. 8, in his 2d report on the geological survey of Penn- 
sylvania ; No. 7 of Mr. Conrad's synopsis of the rocks of New- York, 
in his 2d palssontological report, or as he conceives, the upper part of 
the medial silurian strata of Mr. Murchison. It is also the upper lime- 
stones and water limestone series of Prof. Vanuxem's 2d annual report 
on the geology of New- York. 
The lower strata of this series of rocks consists of various beds of 
common and hydraulic limestones, varying much in thickness and qua- 
lity, even in contiguous quarries. These strata sometimes rest uncon= 
formably upon the Hudson slate group, as at Lawrence's quarry, on 
the Rondout, opposite Wilbur ; sometimes conformably on the Shaw- 
angunk grit, (mill-stone grit of Eaton,) as at Rosendale and Lawrence- 
ville, on the Rondout ; sometimes on the red and variegated shales and 
grits that overlie the Shawangunk grits, as at the High Falls of the 
Rondout, in Marbletown ; and upon the shales and grits of Schenecta- 
dy, and the north part of Schoharie county. 
The following section, most of the details of which were procured 
by Mr, John Gebhai'd, jr. indicates the principal masses of this group 
at Schoharie. 
1. Grey calcareous sandstone, abounding with fossils. 
2. Corniferous limestone, containing many layers and courses of no= 
dules of chert and hornstone, 
3. Cocktail grit of Dr. Eights, characterized by fucoides caudagalli, 
4. Sparry limestone,* highly crystalline in texture, and containing 
many fine fossils. 
5. ^hale. 
6. Pentamerus limestone, capped by a thin silicious stratum, contain- 
ing many fine fossils. 
* This limestone, called by Mr. Gebhard, sparry limestone, is very different in as- 
pect and geological position from that called by this name by Prof. Eaton, Mr. G's. 
sparry limestone will have a suitable name when its fossils shall have been described 
by Mr. Conrad. 
