I20 LOWER PENINSULA. 



The most complete exposure of the carboniferous limestones is 

 seen on Wild Fowl Bay, 6 or 8 miles southwest of Caseville. We find 

 on the shore there, below the water level and emerging above it, a 

 greenish-white calcareous sand rock, visible in a thickness of 4 or 

 5 feet. Next above is a layer of gray limestone with cherty no- 

 dules, about I foot in thickness, overlaid by a thin seam of shale ; 

 then a 6-inch bed of delicately laminated limestone, and a seam 

 of sand rock of a few inches ; on it lie several somewhat differing 

 ledges of an arenaceous limestone of laminated structure, amount- 

 ing to 2 feet, upon which follow in the order given, an 8-inch 

 layer of dark gray bituminous limestone with smooth fracture, a 

 blackish, thinly laminated calcareous shale, 2 feet thick, full of scales, 

 teeth, and bones of small fishes, besides a species of Cypris, or 

 Cythere, and a dark gray limestone of smooth, conchoidal fracture, 

 in three i-foot beds, of which the upper one is pervaded by Syringo- 

 pora-like, fiexuose, anastomosing channels, similar to those already 

 described as existing in several outcrops in other localities. The 

 section is terminated by about 10 feet of light-colored arenaceous 

 limestones, with an alternation of purer calcareous and prevalently 

 sandy seams. These upper beds contain many fossils, Zaphrentis 

 spinulosa, Lithostrotion proliferum, Syringopora ramulosa, various 

 forms of Fenestella, Polypora, etc., Productus, Allorisma clavata, 

 and Fish-teeth (Cladodus, Helodus). The higher levels of the slope 

 are covered by drift. A mile east from the shore, on the farm of 

 Mr. Crawford, and on the adjoining lands forming the plateau of a 

 lake terrace, a series of lime-rock ledges is uncovered, which appear 

 to be the next higher strata to the section just described. The 

 beds are light-colored, pure limestones, occasionally interstratified 

 with a thin seam of sand rock ; certain seams are full of hornstone 

 concretions, while others are quite free of them. Fossils are also 

 very unequally distributed, being rare in scime of the layers, while 

 others are crowded with silicified corals, Lithostrotion proliferum, 

 and Lithostrotion mamillare, which are also found loose, strewn 

 about the fields in immense numbers and beautifully preserved. 



The highest layers found on this plateau are brown, ferruginous, 

 cellulose dolomites of a rough, earthy fracture, irregularly traversed 

 by veins of quartz or calcspar. Further east, the rock ledges dis- 

 appear under heavy drift masses. The purer ledges of the lime- 



