The Echinoid Directory

Glossary

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Glossary terms beginning with: T

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tag
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. (show image)
test
The series of plates that make up the sea urchin skeleton. (show image)
tetrabasal (disc)
An apical disc composed of just 4 genital plates and five ocular plates. Genital plate 5 is missing.
tetrabasal (disc)
tooth
Part of the Aristotle's lantern; the five teeth form the biting tip of the lantern. (show image)
trabeculae
The term applied to the calcitic struts forming stereom. (show image)
tridactylous (pedicellaria)
A kind of pedicellaria with simple rather straight blades and without glands. Blades meet along their distal part. (show image)
trifoliate (pedicellaria)
obsolete name for triphyllous pedicellaria
trigeminate (plating)
A compound ambulacral plate composed of three elements. (show image)
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. (show image)
tube-feet
An external flexible tentacle from the water vascular system. In most echinoids there is one tube-foot to each ambulacral element. (show image)
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. (show image)