Current Action in the Ordorician. — litiedemann. 381 
versally arranged fragments which apparently were arrested 
by the immovable shell, on the east side, and with a drift- 
ridge of longitudinally arranged fragments on the west side. 
2. The motion of the water brought about, in this district, 
the changes in the sedimentation and in the fauna which 
constitute the differences between the Trenton and Utica ter- 
ranes. This assertion is principally based on the following 
observations : 
a. The approach from the Trenton limestone to the Utica 
shale, as well as the lower Utica shale itself are, as described 
before, from the East Canada creek near Dolgeville, marked 
by a regular alternation of beds of limestone and shale, the 
shaly intercalations at first being far apart and thin, but in- 
creasing steadily until the limestone bands dwindle into in- 
significant intercalations and disappear at last entirely. This 
gradual change has already been observed by Vanuxem* on 
the West Canada creek, near Herkimer, and also north of 
Little Falls. It is also observable in the localities south of 
the Mohawk river, where Hallf described Sphenothallus 
(uuiustifolius as being found in the shaly upper Trenton lime- 
stone, near Canajoharie. WalcottJ; reports from the town of 
Deerfield that "the Trenton and Utica formations are inti- 
mately connected lithologically." Prosser§ found sixty feet 
of passage beds, consisting of shale and limestone beds in a 
well at Chittenango, which is south of lake Oneida and west 
of Utica. 
I>. Further, as already observed by Vanuxem and verified 
by Hall II the Trenton limestone and the Utica shale are in the 
state coextensive and concordant. ''The whole of the Utica 
rests upon the Trenton and upon no other rock." (Vanuxem). 
Changes in the depth of the water can not, therefore be ad- 
duced to account for the change in the composition of the 
sediment. 
c. The change in the fauna is gradual, as shown by the 
section near the Flat falls on P^ast Canada creek and gives the 
impression that part of the Trenton fauna,especially the corals, 
~*L. Vanuxem, Nat. Hist, of N. Y.. \A. iii, 18i2, p. 58. 
tJ. Hall, Pal. of New York, vol. i. p. 201. 
tC. D. Walcott, The Utica slate, etc.. Trans. Albany Inst., vol. .\. pn. 
1-17. 
§Ch. S. Prosser. Bull, of Geol. Soc. of Am., vol. iv, p. 91. 
IjProc. Am. Asso. Adv. Sci. 1878, pp. 259-265. 
