Another nacreous formation found in the mother-of-pearl oyster shells is the "blister." It is produced by the raising of the nacreous deposits above the level of the shell to cover some intruder of considerable size. This results in a growth similar in shape to a blister on the flesh, hence the name. It is cut out of the shell and used in various ways as a set for jewelry, or to imitate the bodies of insects or small animals. Others with a slightly higher dome and rounded oval shape, regular in form, are called "turtlebacks." [Illustration: PANAMA PEARL-SHELL, SHOWING MUD-BLISTERS, BORERS, AND PEARL] Some of these hollow shells of pearl have been found to cover small fish, lizards, etc. The writer saw one which appeared to be a large button-pearl. On lifting, it proved to be a shell of several thicknesses of nacre covering a small shell-fish about a half-inch in diameter. The imprisoned mollusk was shrunken and crumbling so that the nacreous covering could be lifted from over it, a hollow dome of pearl. Mud blisters are common in some waters and depreciate the quality of the shell and are otherwise useless. A typical mud-blister appears in the shell illustrated herewith. The Abalone pearl occurs usually as a baroque or blister but occasionally it is found solid and spherical. Although it is not classed among true pearls, a few globular pieces found are entitled to a place among them because they are sometimes identical in construction and have a similar pearly luster, it is however very liable to crack and break and can seldom be pierced with safety. The shell-fish from which it takes the name is the Haliotis, called here the Abalone. It is known under many names—ear-shell, Venus's ear, etc. In the English Channel Islands it is the ormer, and on the adjacent coast of France where it is very abundant the name for it is similar—"ormier." The Aelonians called it the "Ear of Venus." The shell is ear-shaped, flattened, slightly spiral and has a series of round holes near the edge curving with the last whorl toward the boss. As it grows, the oldest of these are successively filled up and the last remaining open, serves as the anal channel. The exterior is very rough and unsightly, but the mother-of-pearl interior is one of the most exquisite pieces of color work painted by the hand of nature and to this is added an enlivening iridescence most fascinating. Like it, the pearl formations are deeply tinted. Brownish reds, peacock greens, and dark grays are the prevailing colors. They are seldom of even color or luster, many of them having but one lustrous point where a pearly glaze seems to have been incorporated with the earthenware like surface.