The costae, longitudinal ribs or rows of spines on the outer surface of the theca.
But in Greek theca (, θήκη) is a place to put something, a receptacle.
These constituted the arms (brachia), and five definite radial plates of the theca were specialized for their support.
This elastic ring is a continuation of the stalk of the theca, which always bursts on the opposite side.
The body is often provided with not-living external formations “stalk” and “theca” (or “lorica”).
This theca grows in the direction of the apex of the sicula, to which it adheres by its dorsal wall.
The theca became sessile, and in its later developments much flattened (fig. 11).
Anus usually in the upper or oral half of the theca, and never aboral.
The pear-shaped body is encased in a theca formed by a number of polygonal plates, and is attached by its narrow end.
A chronic inflammatory involvement of a theca through which an important tendon plays may cause adhesions to form.
theca the·ca (thē'kə)
n. pl. the·cae (-sē', -kē')
A case, covering, or sheath, such as the outer covering of the cocoon of certain insects.