In 1909, Elvira Wood (1865-1928) published A Critical Summary of Troost's Unpublished Manuscript on the Crinoids of Tennessee. On page 93, she names a new crinoid species Hydreionocrinus spinosus after the fossil by Wetherby who described it in 1881 as Hydreionocrinus depressus found by Troost. She writes that Wetherby had actually found a new species and thus she names it. It's genus was later changed to Tholocrinus (Kirk, 1939).
This picture is a recent fossil find from the Glen Dean Member of Grayson County, Kentucky USA. It is a crinoid calyx fossil that appears to be a Pterotocrinus acutus (Wetherby, 1879). The fossil dates to the Mississippian Period.
The most interesting part of the fossil is when it photographed from the top revealing a gastropod was attached to its anal tube when they both died. A somewhat common relationship found in the fossil record between these two creatures.
