The process used at tlie Los Angeles County Museum of Natural History for making casts of fish and reptiles employs neoprene, a white milky liquid, which is poured into molds made of water, clay, such as plaster, hydrocal or ceramic. The advantages of neoprene latex are that specimens may be cast in their entirety, the cast will show extreme detail and no separator is necessary, the cast is tough and flexible, and many reproductions may be taken from the same mold. The chief disadvantages are that cured neoprene will turn brown if exposed to strong light for long periods of time. As in most water dispersed compounds, neoprene latex casts have approximately 7% uniform shrinkage.