Maryland Geological Survey 33 



1842 and the name " New York Transition System " was used for the 

 " series which fill up the space between the Primary and the Old Red 

 System." ^ This system was divided by Dr. Emmons into four groups 

 which, arranged in ascending order, he characterized as follows : " Cham- 

 plain group, at the base of the Transition system; Ontario group, com- 

 prehending the rocks which lie upon its southern border for about 15 

 or 20 miles; the Helderberg series: and lastly, the Erie group, which 

 completes the whole series of the system, extending up to the old red 

 sandstone." * The limits of these groups are not clearly indicated in 

 this part of the report; but it appears probable that the upper limit of 

 the Helderberg group was placed at the top of the Upper Helderberg or 

 Onondaga limestone and that the Erie group included the rocks from the 

 base of the Marcellus shales to the top of the Chemung. At the close 

 of the report is given a " Tabular view of the sedimentary rocks of New 

 York " ' in which appears the " New York system " composed of the 

 four groups named in the earlier part of the report, while the limits of 

 the Helderbei'g and Erie groups are clearly shown to be as above stated. 

 The Devonian rocks of New York, however, are most typically developed 

 in the central and western parts of the state which formed the Third and 

 Fourth Geological Districts. The final report of the Third District by 

 Lardner Vanuxem, which covered central New York, also appeared in 

 1842 and in this the classification of Dr. Emmons, though somewhat 

 modified, was adopted." All the sedimentary rocks of the district, with 

 the exception of the Quaternar}' and some beds referred to the Taconic 

 system, were given under the " New York System " which was composed 

 of five divisions named in ascending order the Champlain, Ontario, 

 Helderberg, Erie, and Catskill. The Helderberg division included all 

 the rocks from the base of the " Onondaga salt group " to the top of the 

 " Corniferous limestone " ; while the Erie division contained the Marcellus 



' Geology New York, Pt. II, p. 99. 



''/bid., p. 100. 



= IMd., p. 429. 



* Vanuxem's statement regarding the general classification of the New York 

 rocks is that " the views of Dr. Emmons were cordially embraced and adopted 

 with some modifications" (Geology of New York, Pt. Ill, p. 12). 



