Lias

li'as, in geology, a rock formation. It consists chiefly of grayish limestone, shales, and marlstones. It is characterized by a wealth of fossil remains, especially ammonites and other shells. The lizard-like animals known as the ichthyosaurus (ik-thi-o-sau'-rus) and the pleiosaurus (pli-o-sau'rus) are found in this formation. The lias is particularly well developed in England. It is found on adjacent parts of the continent. It the United States a similar formation occurs in Oregon and California. Lias quarries have a peculiarly striped appearance, owing to the occurrence of layers of differently colored rocks.