Here are some illustrations of the brachiopod fossil
Orthothetes subplanus (Conrad). The fossil was found in the Clinton beds at Niagara Falls, New York, USA. The fossil dates to the Silurian Period. This fossil is also found in the Rochester Shale. They were published in
Amadeus Grabau's (1870-1946) book
Geology and Palaeontology of Eighteen Mile Creek and the Lake Shore Sections of Erie County, New York from 1899. The images are from page 184, figure 91.
