30 Some Geological Problems — Calvin. 
son's Quarry, Atalissa and all other points where limestone con- 
taining Spirifera parryana is exposed. 
The yellow sandstones above the mouth of Pine creek there- 
fore are of the same age as the limestones near Buffalo. They 
are not even Chemung unless the limestones are also Chemung; 
much less are they Lower Carboniferous or Kiuderhook. 
Owen gives a recogaizable figure of Spirifera parryana as it 
occurs with the shell preserved in the Hamilton limestones 
along Pine creek, and another figure of a cast of the same 
species as it occurs in the overlying sandstones.* Both forms 
are described as Spirifera euruteines, but it is interesting to 
note that the specific identity of the two forms is distinctly rec- 
ognized, and that furthermore the beds containing them are 
referred to the same period. 
No Kinderhook or Sub-carboniferous of any kind has been 
observed by the writer in the reg'on about Pine creek in Mus- 
catine county. A very complete section of the rocks of the 
region may be studiel in the bed and banks of Robinson's 
creek, a small stream emptying into the Mississippi a short dis- 
tance below Montpelier. Near the mouth of the creek is the 
ledge of limestone already mentioned as exposed at low water, 
and extending out into the river for more than a hundred 
yards. This limestone is the sauie as that found at Hanson's 
quarry, Pine Creek mills and many other points, and is char- 
acterized by the presence among others of the following fossil 
species: Spirifera parryam, S. aspera, Atrypa reticularis, 
and Aihyris vittata. Following up the channel of Robinson's 
creek we find, — 1, beds of arenaceous shale with some thin beds 
of limestone, containing branching polyzoa, Atrypa reticularis, 
Strophodonta demissa, very large forms, and Orthis iowensis-^ 
— 2, argillaceous shale only a few feet in thickness and contain- 
ing no fossils; — 3, layers of sandstone among which is a bed 
about 14 inches in thickness containing casts of Spirifera par- 
ryana, {S. capax) with which are associated either in the same 
bed or in adjacent beds both above and below, casts of Atrypa 
reticularis, Strophodonta demissa, Orthis iowensis, and Spiri- 
♦Owen's Geological Survey of Wisconsin, Iowa and Minnesota, Table 
III, figs. 2 and 6, 
tNo opportunity has yet been found to measure the thickness of the 
several 'members of the section. 
