Argillaceous Oxide of Iron

My very good friend the Rev. J. Harriman sent me this from the banks of the river Tees, which place seems to abound in a great variety of curious petrifactions. It appears to be a fragment of a large flat piece of a confirmed Iron-stone, and, I should suspect, a very good one of the kind. It is however rendered additionally curious, as it includes Carbonate of Lime, or Calcareous Spar, in the form of Echinus spines, but different from any before noticed.