Spirifer consobrinus is a fossil that is confined to a specific strata within the Windom shale at Penn Dixie and 18 Mile Creek in New York. It's a small brachiopod that resembles Mucrospirifer but has a much shorter hinge line and a larger interarea on the pedicle valve. The pedicle valve's "beak" is also recurved more strongly. It has taken me a few years to really figure this out and I only have a handful of decent specimens.
Spirifer consobrinus is well documented in Amadeus Grabau's book "Geology and Paleontology of 18 Mile Creek". It's lends it's name to a zone (layer or bed) within the Windom Shale. The zone is found "two to five feet above the Encrinal Layer" (the Encrinal Layer is now called the Tichenor Limestone). The Windom shale is part of the Moscow Formation and is Devonian (Givetian stage) in age.