If its Paleozoic, there are few possibilities for the age. It could be Mississippian (Early Carboniferous) limestone, similar to the one which makes up Wind Cave in the Black Hills, much farther west. But more likely I think it could be the Cambrian Deadwood Formation, which is most common in the Black Hills, but is found as far northeast as North Dakota and Manitoba. However if these are echinoderms, I think that they are much more likley middle Palezoic crinoids, than Cambrian eocrinoids or cystoids. The most likley possibility is that if its Palezoic and echinoderm, than its probably Orodvician, a small remainder of the Pleistocene glacier carving.