80 REPORT OF THE 



opment, while, in the State of New York, the source of the 

 materials seems to have been from the east. 



11. — Marshall Group. 



In Huron county, we find the gritstones separated from 

 the higher sandstones by a conglomerate about two feet 

 in thickness, in which occur some of the fossils of the over- 

 lying group, especially a Bhynchonella of undescribed spe- 

 cies, which, in some localities, forms entire masses of rock. 

 From the grindstone quarries to Point au Chapeau, the coast 

 is occupied by sandstones which, at the* various " Points " 

 rise m bluffs from eight to twenty feet high, and farther 

 back from the shore attain, in some instances, considerable 

 elevations. The distinction between the Marshall and Na- 

 poleon Groups is not clearly traced along this coast. At 

 Hard Wood Point, three-fourths of a mile west of Pt. au Pain 

 Sucre, (called also Flat Rock Point,) are seen, proceeding from 

 the west, the first undoubted fossils of the Marshall Group. 

 The rock here, which rises but a few feet above the surface, is 

 a fine grained, bluish sandstone, with minute glistening scales 

 of white mica. It embraces a Nucula characteristic of the 

 Marshall sandstone, a Solen, a Clymenia and a Goniatites. The 

 Clymenia occurs in a purplish, fine grained sandstone of ex- 

 ceeding hardness, equaling, in this respect, the Medina Sand- 

 stone. In a specimen of the rock found here, containing car- 

 bonaceous specks, were seen small geodes lined with rusty 

 crystals of calcareous spar, and containing small imbedded 

 crystals of native copper. 



Between this locality ana" Flat Rock Point, the section near 

 the shore reveals several feet of purplish, greenish and yellow- 

 ish strata, success'vely lower in the series, in some of which I 

 recognized a minute Cypris-Wko, shell similar to one seen at 

 numerous points in the southern part of the State. At Flat 

 Rock Point, still lower mcks rise ten feet above the water, 

 characterized by oblique lamina?, of great extent and unifermity, 

 dipping 45° toward N. 38° E. The whole rock here is a purely 



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