38 NEW YORK STATE MUSEUM 



passage from the Lower Medina to Hudson is imperceptible, 

 and the red or brownish red shales yield Am b onychia 

 r a d i a t a and Rhynchonella capax." 



Stevenson regarded the Oneida as below the Medina, but 

 mentions the fact that the Oneida at this locality is absent and 

 that the conditions as above stated prevail. 



In Ohio and Indiana, the Richmond beds follow the Lorraine. 

 The Richmond beds are fossiliferous and their fauna contains a 

 number of Trenton forms. If we regard the Oswego sandstone 

 as following directly the Lorraine in New York State, then the 

 Richmond must, in part at least, be the time equivalent of the 

 Oswego sandstone.^ 



At present the Oswego sandstone is regarded as Ontaric and 

 the Richmond beds as Champlainic. 



It is generally held that the Champlainic period was brought 

 to a close by the Taconic revolution. In eastern New York 

 the entire portion became land, but deposition continued in the 

 vicinity of Oswego county, since the Oswego sandstone follows 

 the Lorraine without break. 



If we consider the Champlainic as being brought to a close 

 with the beginning of the Taconic revolution, then the Oswego 

 sandstone could be made, as it is at present, the base of the 

 Ontaric.^ The Oswego sandstone is practically without fossils, 

 so from a basis of paleontology alone it can not be correlated 

 with the Richmond beds. It seems, however, that the Oswego 

 sandstone represents a near shore condition which was unfavor- 

 able for the existence of life but farther west the Richmond 

 fauna flourished under more suitable conditions. The very 

 marked paleontologic break at the close of the Lorraine is 

 another factor in favor of making the Ontaric begin at the base 

 of the Oswego sandstone. 



The absence of a Richmond fauna from this section of New 

 York is then to be accounted for by the changes in conditions of 

 sedimentation rather than by an hiatus at the close of Lorraine 

 time. There is a possibility that a fauna closely allied to that 

 of the Richmond may yet be found in New York, in which case 

 it would have an important bearing on the subject. The pres- 

 ence of such a fauna, however, is considered not very probable. 



^See Pal. Minn. 1897. v. 3, pt. 2, p. ciii. 



Note. — Grabau states, "If no unconformity exists between the Upper Richmond and the 

 Mayville beds and if the latter are of the age of the Clinton of New York, the lower Medina 

 shales of the Niagara region resting upon the Lorraine, must be of Richmond age." N. Y. State 

 Mus.Bt1l.g2. 1906. p. 124. 



*The value of subsidences and emergences as a basis for stratigraphic classification is stated 

 by Ulrich and Schuchert in the annual report of the New York State Paleontologist for 1901, 

 p. 6s9. 



