102 EEPOET OF THE 



whitish or grayish color. The laminae extend from top .to 

 bottom of the mass, dipping north-west at an angle of about 

 45°. They are quite undulating and even contorted, and the 

 whole mass shows something of a rude concretionary structure. 



The formation strikes the main land at Point au Gres. The 

 rock here, in spite of the name, is a limestone. That part of 

 •the outcrop above the water consists of three layers, eaeh about 

 15 inches thick. The upper layer is, in places, quite arena- 

 ceous, but is more solid than the rock at Cheboyong creek. It 

 contains stains of greenish matter and irregulatly cylindrical, 

 somewhat concretionary, bodies, considerably colored. Here 

 occurs the Syringopora which occupies the top of the section at 

 Wild Fowl Bay. This layer is separated from the next by two 

 or three inches of laminated, argillo-calcarcous sandstone. 



The middle layer is more purely calcareous, but contains 

 some sand. Here I saw an Acervidaria, a Syringopora, a Gy- 

 athophylloid, and the remains of a bony body, whose impression 

 left pits regularly disposed upon the rock. 



The lower layer abounds in concretionary cherty nodules, 

 perforating the rock in every direction, often appearing, when 

 broken at the surface of the stratum, like plugs driven into the 

 rock. These nodules are less flinty than those seen at Wild 

 Fowl Bay. 



A large Productus was picked up on the beach. 



Between this point and Newaygo county, no definite informa- 

 tion has yet been collected respecting this formation. We 

 know from the surveyors' notes, that limestone outcrops at 

 various points, but I have seen no specimens, and its geologi- 

 cal characters are in doubt 



' The thickness of this formation is much greater on the west- 

 ern (and probably northern) borders of the basin, than on the 

 southern. It is 51 feet thick at Scribner's well at Grand Eapids, 

 and the whole thickness in this vicinity is probably not less 

 than 70 feet. It is found 65 feet thick in the salt wells of East 

 ' Saginaw. 



As this calcareous member of the Carboniferous system pos- 



