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Are muscles with circular fibres surrounding some natural opening of the body. 1. Orbicularis seu Constrictor Oris, Sphincter Labiorum, Semi seu Demi-orbicularis, Supra-semi-orbicularis, Labialis, Osculatorius, Basiator, (F.) Labial, Orbiculaire des levres. A muscle situate in the substance of the lips, and extending from one commissure to the other. It is formed of two very distinct portions, of a semi-oval shape; one belonging to the upper lip, the other to the lower. Their extremities cross at the commissures, and are confounded with the other muscles of the parts. The use of this fleshy muscle is to bring the lips together, and to close the aperture of the mouth, by making it represent a sort of bourrelet with radiated wrinkles. It is an antagonist to every other muscle of the lips. 2. Orbicularis Palpebrarum seu oculi seu palpebrarum ciliaris, Palpebrarum duo musculi, Palpebralis, Constrict or seu Sphincter Palpebrarum seu Oculi, (F.) Naso-palpebral (Ch.), Maxillo-palpebral, Palpebral, Orbiculaire des paupieres. A muscle common to both the eyelids, and seated in their substance. It is broad, thin, transversely oval, and cleft in its great diameter It is attached to the nasal process of the superior maxillary bone; to the internal angular process of the frontal bone, and to the orbitar process of the superior maxillary bone. From these origins the muscle passes outwards, under the skin of the eyelids, surrounding the orbit in a circular manner, extending somewhat beyond it, and covering the upper part of the cheek. It is inserted into the skin of the eyelids, its upper and inner edge being intimately connected with the frontal and corrugator muscles. Its use is to close the eye, by bringing the eyelids together. The part of the orbicularis which covers the cartilages of the eyelids, and which is remarkably thin, is the Musculus Ciliaris of some authors.