eios_, perfect; _saura_, lizard). An extinct
genus of Crocodilian Reptiles.

TELEOSTEI (Gr. _teleios_, perfect; _osteon_, bone). The order
of the "Bony Fishes."

TELSON (Gr. a limit). The last joint in the abdomen of _Crustacea_;
variously regarded as a segment without appendages, or as an
azygous appendage.

TENTACULITES (Lat. _tentaculum_, a feeler). A genus of _Pteropoda_.

TEREBRATULA (Lat. _terebratus_, bored or pierced). A genus of
_Brachiopoda_, so called in allusion to the perforated beak of
the ventral valve.

TEST (Lat. _testa_, shell). The shell of _Mollusca_, which are
for this reason sometimes called "_Testacea_;" also, the calcareous
case of _Echinoderms_; also, the thick leathery outer tunic in
the _Tunicata_.

TESTACEOUS. Provided with a shell or hard covering.

TESTUDINIDAE (Lat. _testudo_, a tortoise). The family of the
Tortoises.

TETRABRANCHIATA (Gr. _tetra_, four; _bragchia_, gill). The order
of _Cephalopoda_ characterised by the possession of four gills.

TEXTULARIA. (Lat. _textilis_, woven). A genus of _Foraminifera_.

THECA (Gr. _theke_, a sheath). A genus of Pteropods.

THECODONTOSAURUS (Gr. _theke_, a sheath; _odous_, tooth; _saura_,
lizard). A genus of "Thecodont" Reptiles, so named in allusion
to the fact that the teeth are sunk in distinct sockets.

THERIODONT (Gr. _therion_, a beast; _odous_, tooth). A group of
Reptiles so named by Owen in allusion to the Mammalian character
of their teeth.

THORAX (Gr. a breastplate). The region of the chest.

THYLACOLEO (Gr. _thulakos_, a pouch; _leo_, a lion). An extinct
genus of Marsupials.

TRIGONIA (Gr. _treis_, three; _gonia_, angle). A genus of Bivalve
Molluscs.

TRIGONOCARPON (Gr. _treis_, three; _gonia_. angle; _karpos_,
fruit). A genus founded on fossil fruits of a three-angled form.

TRILOBITA (Gr. _treis_, three; _lobos_, a lobe). An extinct order
of _Crustaceans_.

TRINUCLEUS (Lat. _tris_, three; _nucleus_, a kernel). A genus
of Trilobites.

TROGONTHERIUM (Gr. _trogo_, I gnaw; _therion_, beast). An extinct
genus of Beavers.

TUBICOLA (Lat. _tuba_, a tube; and _colo_, I inhabit). The order
of _Annelida_ which construct a tubular case in which they protect
themselves.

TUBICOLOUS. Inhabiting a tube.

TUNICATA (Lat. _tunica_, a cloak). A class of _Molluscoida_ which
are enveloped in a tough leathery case or "test."

TURBINATED (Lat. _turbo_, a top). Top-shaped; conical with a round
base.

TURRILITES (Lat, _turr