Blastoid (blas'-toyd) fossils commonly are called "sea buds." They are closely related to crinoids but differed in that, instead of arms, blastoids had long hair-like brachioles that swept food into the mouth. The delicate brachioles rarely were preserved.
Like crinoids, blastoids had a mouth at the top of the body (calyx) surrounded by small round holes that conducted food particles into and wastes out of the body.
Blastoids are beautiful fossils that look much like small hickory nuts. They most commonly are found in the river cliffs and stream banks of western and southwestern Illinois, especially in Randolph County, and in southern Illinois near the Ohio River.