. The Canadian field-naturalist. Natural history. 14 The Ottawa Naturalist [Vol. XXXII. 5. Yellow unfossiliferous shaly lime- stone 1 4. Hard, brittle, unfossiliferous grayish limestone 1 3. Limestone similar to the above in ap- pearance, but very shaly 2. Thickly bedded gray buff limestone- 1 1. Heavy yellowish buff to brownish limestone very coarse and apparently unstratified. Porous with large amounts of calcite, and often much broken in portions, unfossiliferous. To bed of creek 3 same as those shown at the Bloody Run section and 4 the relative position is the same. In Charles City the mud
. The Canadian field-naturalist. Natural history. 14 The Ottawa Naturalist [Vol. XXXII. 5. Yellow unfossiliferous shaly lime- stone 1 4. Hard, brittle, unfossiliferous grayish limestone 1 3. Limestone similar to the above in ap- pearance, but very shaly 2. Thickly bedded gray buff limestone- 1 1. Heavy yellowish buff to brownish limestone very coarse and apparently unstratified. Porous with large amounts of calcite, and often much broken in portions, unfossiliferous. To bed of creek 3 same as those shown at the Bloody Run section and 4 the relative position is the same. In Charles City the mud-crack horizon may be found in places below 6 great beds of the stromatoporoids and beneath the water level of the Cedar river. At Cedar Rapids, 10 in Linn county, the writer observed what was taken 2 to be a continuation of this horizon though he can make only a provisional statement that it occurs there. Mr. Webster considers that this horizon ex- tends even to the south of Cedar Rapids. The most satisfactory localities for the study of this horizon are the two Bloody Run quarries. The 1 bed in these quarries has been exposed for a long. Fig. 1, A and B—Mu<l-craek: the smaller specimen (A) sliows tlie first type: tlie larger one ( B) shows that of the second. Specimens in collcctioii of Carroll T.,miic Ki'iiton. Bed number 12 of this section has the widest extension of any mud-crack horizon of the Iowa Devonian known to the writer. It is found at var- ious points cast of Charles City, at Devonia, in the north part of Floyd county, at and near Osage and Mitchell in Mitchell county, and in other localities in the northern portion of Floyd as well as in portions of Cerro Gordo and Worth counties (C. L. Web- ster). At Waterloo, in Blackhawk county, it is a continuous horizon, and south of the State Teachers' College at Cedar Falls it is also well developed and has a good exposure on the bank of a small creek. The characters at these localities are practically the term of yea
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