Some Geological Problems — Calvin. 31 
fera aspera; — 4, a considerable thickness of sandstones con- 
taining no fossils as far as observed; — 5, arenaceous beds con- 
taining casts or impressions of corals related to Cladopora, 
and impressions of what seem to be immense masses of Stro- 
matopora; — 6, a bed of fragmentary materials interstratified 
with irregularly interrupted flexuous beds of shale and sand- 
stone, varying greatly in thickness and spread over the uneven 
and apparently eroded surface of the underlying sandstone; — 7, 
flexuous beds of shale, with a bed of impure coal from two to 
three feet in thickness; — 8, evenly bedded friable sandstone 
varying in color from yellow to gray, and containing in some of 
its layers numerous impressions of Calamites, Sigillaria and 
Lepidodendon. Casts of the stems of Lepidodendon, apparently 
of the species recognized by Owen as L. aculeatum Sternberg,* 
were observed more than nine inches in diameter. 
The beds i-5 are of Devonian age and must all be referred 
to the same period as the limestones at Buffalo and Pine creek 
Mills. Beds 6, 7 and 8 are of much later origin; they belong 
to the Carboniferous period and were probably contempora- 
neous with the upper Coal Measures of southwestern Iowa. 
Practically the same succession of strita as seen in Robin- 
son's creek, may be observed in what is know as the railrcad 
quarry at Montpelier. An immense quantity of stone was 
taken out by the railway company and used as riprappiug to 
protect the embankment from the wash of the river. The 
magnitude of the work performed here may be inferred from 
the fact that the riprappiug extends, sometimes for miles con- 
tinuously, as far as Muscatine, a distance of sixteen milea. 
The beds worked were Devonian sandstone, the equivalents of 
3, 4 and 5 of the section on Robinson's creek. The spirifer- 
bearing layer is here about two feet in thickness; it is harder 
than at the localities on Robinson's creek or on the river above 
the mouth of Pine creek, and it would seem to have furnished 
a very large proportion of the material used in riprappiug. At 
the upper end of the quarry, coal-measure shales and sandstones 
are seen resting unconformably on the Devonian saudstones. 
The lower beds are very flexuous and distorted. A well mark- 
ed layer at any point may thin out and disappear in a distance 
♦Owen's Geological Survey of WiBCOnsin, Iowa and Minnesota, Table 
VI, figs, 1 and 2. 
