34 LOWER PENINSULA. 



quarry are bluish gray dolomites in moderately thick ledges, 

 opened to the depth of about eight feet, and representing the 

 principal quarry-stone used for ordinary building purposes. In 

 the M'hole series of rock beds, fossils are rarely seen, but in nests or 

 in a thin scam, locally, they may be found in abundance. Among 

 the rocks which came out on excavating the cellar of a brewery 

 situated within the quarry, certain blocks are crowded with casts 

 of Meristella la;vis, Retzia globosa, Leptocoelia concava, Megam- 

 bonia aviculoidea and several other bivalves, several Gastero- 

 pods, great numbers of a spirorbis-like shell, besides the vegetable 

 stems found elsewhere in the same strata. 



In the southwest corner of La Salle town, about six miles west 

 of the lake shore, the brecciated limestones, which in Monroe are 

 in a position on a line with the lake level, are found in the quar- 

 ries at an elevation of about lOO feet above the lake. 



In the quarries near Little Lake, in Bedford township, simi- 

 lar strata to those of the Plum Creek quarries are uncovered. In 

 the upper part of the quarry we find an oolith stratum identical 

 with the one in the other locality. The lower part is formed 

 of brecciated limestones, seams of which are fossiliferous ; be- 

 sides the already-mentioned forms, a Cyrtoceras and some Gaste- 

 ropod casts are found there, which I have not noticed in the other 

 localities. 



Two miles west of Ida village, close to the railroad track, exten- 

 sive quarries are opened and lime-kilns erected. Close under the 

 surface, light-colored, almost white dolomites, of finely crystalline 

 grain, and of absorbent, porous structure are found ; they are much 

 intersected by veins of calcspar, and inclose druse cavities lined 

 with the same material. Certain layers are completely filled with 

 small acicular spar crystals, or the crystals have been dissolved by a 

 partial weathering of the rock, and the places formerly occupied 

 by them are now found as open, narrow slits pervading the rock in 

 all directions. By the same process of weathering, the rock, which 

 originally was a hard mass composed of dolomite spar crystals, 

 cemented together by calcspar, the more soluble calcspar being 

 dissolved by the percolating waters, is left, according to the degree 

 of weathering, either a porous but yet hard mass of minute do- 

 lomite spar crystals, or a mealy, crystalline substance friable be- 

 tween the fingers. 



