It originates at the arch of the ischium and extends forward between the thighs.
"Common Diseases of Farm Animals"
R. A. Craig, D. V. M.
The furculum, or merry-thought, which is entire, marks the fore part of the trunk; the ischium, scapula, and most of the wing and leg bones are preserved, and there are impressions of the quill feathers and of down on the body.
"The Antiquity of Man"
Charles Lyell
Fracture of the ischium alone is rare.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson