A smooth, slightly elevated, tongue-like flange that borders the buccal notch and runs along the adradial margin of interambulacral plates. It supports the buccal sacks.
test
The series of plates that make up the sea urchin skeleton.
tetrabasal (disc)
An apical disc composed of just 4 genital plates and five ocular plates. Genital plate 5 is missing.
tooth
Part of the Aristotle's lantern; the five teeth form the biting tip of the lantern.
trabeculae
The term applied to the calcitic struts forming stereom.
tridactylous (pedicellaria)
A kind of pedicellaria with simple rather straight blades and without glands. Blades meet along their distal part.
trifoliate (pedicellaria)
obsolete name for triphyllous pedicellaria
trigeminate (plating)
A compound ambulacral plate composed of three elements.
triphyllous (pedicellaria)
A kind of pedicellaria with small, leaf-like blades.
triserial
Arrangement of pore-pairs (tube-feet) forming three separate series in each half-ambulacrum.
tube-feet
An external flexible tentacle from the water vascular system. In most echinoids there is one tube-foot to each ambulacral element.
tubercle
A knob-like projection on the plate surface that bears a spine. Unlike granules, tubercles have a distinct mamelon on which the spine articulates.
