566 PROCEEDINGS OF THE ACADEMY OF [DeC, 



Criss Creek by Luther whose interpretation of its section seems 

 to be as follows: The hard layer producing the falls near the lake 

 road bridge is "Near the top " of the " Cardiff. " A " gray f ossilif erous 

 band at the base of the formation" Avhich occurs at the private road 

 crossing farther north is attributed to the horizon of the Stafford 

 limestone of western New York. 



The present writer's interpretation of the same section may be 

 summarized in this way: The hard layers making the falls near 

 the lake road bridge are the upper limy portion of the Mottville. 

 They are underlaid by about 15 feet of gray shale rich in small 

 fossils. These latter are the lower soft shales of the Mottville and 

 are considered the equivalent of strata which on the Tully quad- 

 rangle have been assigned to the Skaneateles by others. A short 

 distance below the lake road bridge their contact with the under- 

 lying black Marcellus is well displayed. The "gray fossilif erous 

 band" exposed near the private road crossing farther down stream 

 is not connected by continuous section with the Mottville at the 

 lake road bridge. It has the same lithologic and paleontologic 

 characters as the lower 15 feet of Mottville at the lake road bridge. 

 It is also immediately overlaid by material indistinguishable from 

 the harder Mottville, while a short distance still farther down stream 

 another exposure of typical Marcellus is found. It is believed that 

 the lakeward dip which is plainly visible in places and a slight folding 

 are responsible for the repetition of the strata. 



This latter interpretation is amply confirmed by a study of the 

 lake shore sections east and west of the Lehigh Valley track between 

 Levanna and Farley's. It also appears to be in harmony with the 

 section of the region which was published by. Cleland in 1903.^^ 



Summary of Observations. 

 The writer believes that the following points have been demon- 

 strated : 



(1) That the Marcellus black shale is continuous from the Tully 

 quadrangle to the east shore of Cayuga Lake (as stated in sul)stance 

 by Vanuxem) and that it thins considerably to the westward. 



(2) That the Cardiff shale, as' defined by its authors, thins rapidly 

 toward the west and becomes unrecognizable as a separate unit 

 before the Auburn quadrangle is reached. 



(3) That the Mottville member (basal Skaneateles of the Tully 

 quadrangle) is continuous throughout the region, lying on the 



» U. S. G. S. Bulletin 206, p. 21, fig. 2. 



