Thumb, n. In birds, the so-called thumb, upon which the alula, or bastard wing, grows, is homologically the index-finger. Penguins lack this segment.

Thyrohy´al, n. An element of the hyoid bone.

Thy´roid, a. Shield-shaped. Name of principal laryngeal cartilage.

Thy´roid Car´tilage. One of those forming the larynx.

Tib´ia, n. Principal and inner bone of leg between knee and heel; the shin-bone.

Tib´ial, a. Pertaining to the tibia.

Toe, Toes, n. (116.)

Tomium, n.; pl. tomia. The cutting edge of the bill. There is a superior or maxillary tomium, and an inferior or mandibular tomium; each is double (i.e. right and left); together they are the tomia, mutually apposed when the mouth is shut.

Top of Toes. (117.) See Acrodactylum.

Tor´quate, a. Ringed; collared.