SECTION OF) TEE MANETUS: -EIMESTONED Xie edb, 
NORTHERN END OF THE HELDERBERG PLATEAU 
CHARLES S. PROSSER 
Ohio State University 
The Helderberg Mountains, or more properly plateau, form a 
prominent topographic feature of eastern New York the northern 
escarpment of which is very conspicuous to the south when traveling 
by electric or steam car between Schenectady and Albany. 
Stratigraphic geology in America had its beginning in Albany 
and Schoharie counties, New York, so that for many years the 
Helderbergs have been classic ground for geologists. Near the 
northern end, about south of Meadowdale on the Delaware & Hudson 
railroad, a highway known as the Indian Ladder road climbs the 
steep escarpment and this section has been visited and studied by 
many geologists. Several years ago the writer described this section;* 
but at that time the limestones forming the conspicuous cliff were 
known as the Tentaculite and Pentamerus. It was attempted to 
separate these two formations according to the original definition of 
Gebhard and later description of Mather; but since the line of 
division was not very clearly indicated in the original description 
perhaps the writer was not altogether successful in locating the line 
of separation used by those early geologists. After the preparation 
of my paper, geographic names were substituted for those based 
upon the generic names of inclosed fossils and Vanuxem’s ‘‘ Manlius 
water-lime group,”’ shortened to Manlius lmestone, replaced the 
Tentaculite limestone, and the new name of Coeymans limestone 
was proposed to replace the Pentamerus.? Later, Professor G. D. 
Harris studied the Helderbergs and published a general section, 
‘based largely on the outcrops near Indian Ladder,” together with 
four special sections. Mr. Christopher A. Hartnagel, assistant 
« Kighteenth Ann. Rept. State Geologist [N. Y.], pp. 53-50. 
2 Science, IN. S., Vol. X,; Dec, 1890, pp. 876, 377. 
3 Bull. Am. Paleontology, No. 19, 1904, Pl. 1, and pp. 24-26. 
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