198 Thirty-fifth Keport cm the State Museum. 



Contrary to statements heretofore made, the Chemung group does 

 not appear in either Starkey or Barrington. The coarse, easily-broken 

 sandstones of the lower Chemung are readily distinguished from the 

 fine-grained and tougher Portage rock, even in the absence of fossil 

 remains; and in Italy hollow where the junction of the two forma- 

 tions may be seen, the difference is very perceptible. 



Portage Group. 



The greater part of Yates county is occupied by the Portage group. 

 The lower portion of the group contains much iron pyrites and is di- 

 vided into thick, solid strata of sandstone separated by shaly-beds. 

 The sandstone is quarried in many places and forms a valuable build- 

 ing material. 



We give herewith a cut showing evidence of disturbance as seen in 

 the "Big gully." 



Section in "Big Gully." 



Fig. 6. — a. Stratum of gypsiferous rock, 1£' thick, b. Portage group. 



In the southern part of Milo, on the farm of Mr. Valentine, there 

 is a large area of naked rock, or covered in places with a few inches 

 of soil. Here is a fine exhibition of glacial action in the polished 

 and grooved surface. Some of the striae are of considerable depth 

 and all parallel. Deposits of tufa and travertine are found in moist 

 ravines in this group. Concretions of various sizes and shapes are 

 common and often mistaken for petrifactions. Small cubical crystals 

 of iron pyrites (" fool's gold ") are not uncommon in some places. 



Fine water-falls occur m several places. In Eggles ton's gully, in 

 Barrington, there is one of one hundred feet, in one unbroken descent. 

 Some very good examples of ripple-marks or mud-waves may here be 

 seen. In Bruce's gully, in Milo, are two falls of sixty and forty feet 

 each. Here, in Bruce's gully, about forty feet from the base of the 

 Portage, Dr. S. Hart Wright found a fossil, which Dr. J. S. Newberry 

 pronounces the only Devonian representative of Agassiz's genus Pris- 

 tocanthus he knows of. 



