Crinoid Calyx (SiO2 Pseudomorph)

[Thebes]

Presumably, having been tumbled along the robustness of the Knob Creek's quartz bearing country rock of the Hoosier National Forest in the Bartlettsville (North Lawrence Co.) IN area, the tip of the Crown (Calyx) of this large Crinoid appears to have been sheered off at some point to give the observer a view (in crossection) of the inside of calyx which reveals absolutely nothing but Silica replacement of all internal parts.  This sample is of the Harrodsburg Formation in the Sanders Group, Lower Middle Mississippian Time.