Crinoids usually have a stem used to attach themselves to a substrate, but many live attached only as juveniles and become free-swimming as adults. They are very fragile and require specific ...

American Indians used chert for tools and weapons. Crinoids are marine animals that look like flowers. It has a long stem or stalk and a series of petal-like tentacles. The stalk keeps the animal ...

Fieser, L. F., and Fieser, M., Natural Products Related to Phenanthrene (third ed.), 204 (Reinhold, New York, 1949). Fieser, L. F., and Fieser, M., Steroids, 177 ...