STATE GEOLOGIST. 13 



XXIII. Gray and yellow sandstone. (Hubbard, 1841, p. 128.) 

 XXII. Shales and coal of the " lower coal measures." (Doug- 

 lass, 1840, p. 65 ; Hubbard, 1841, p. 126.) 

 XXI. Blue, compact, slaty sandstone. (Hubbard, 1841, p. 



136.) 

 XX. Gray limestone, or Upper Limerock — 14 ft. (Hubbard, 



1841, pp. 125-130r) Douglass places this between 

 the "Upper" and "Lower Coal," and says the Gyp- 

 sum is above, or embraced in it. (1840, pp. 62-61.) 

 The Gypsum is also placed above by Houghton. 

 (1839, p. 11.) 

 XIX. Fossiliferous ferruginous sandstones. (Hubbard, 1840, 

 pp. 81-88.) Thinned out at Grand Eapids. (Hub- 

 bard, 1841, p. 138.) Subdivided as follows : 

 G. Coarse, quartzose, yellowish gray sandrock, 30 ft. 

 P. Ash colored, or brown sandrock, with marine 



fossils, 15 ft. 

 E. Dingy and green, finegrained strata, with occasional- 



_fossils and ferruginous spots. 

 D. Hard gray stratum of sandrock, 1 ft. 

 0. Dingy-green, finegrained sandstone, interstratified . 

 with slaty sandstone, and apparently with blue 

 clay shale, 15 to 20 ft. 

 B. Yellow, fossiliferous sandrock. Abounds in marine 

 fossils. 20 ft. 



A. Finegrained sandrock. 



XVIII. Kidney Iron Formation, 45 ft. (Hubbard, 1840, p. 86 ;'. 



1841, p. 13; Houghton, 1840, p. 25.) Considered. 



the bottom of the Carboniferous System. 

 XVII. Sandstone of Pt. aux Barques. Passes south-west 



and underlies the sandstone of Hillsdale county, 



though not exposed there. (Hubbard, 1841, p. 132.)' 



Divided as follows : 



B. Coarse sandstone or partial conglomerate. (Hub- 



bard, 1841, p. 136.) 



