80 REPORT OF THE 



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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 ©f the fossils of the over- 

 lying group, especially a Ehynchonella of undescribed spe- 

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

 Prom the grindstone quarries to Point au Chapeau, the coast 

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

 rise in 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 Eock 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 

 Clyvienia 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 and 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-like shell similar to one seen at 

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

 Ruck Point, still lower rocks rise ten feet above the water, 

 characterized by oblique laminEe of great extent and uniformity, 

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



