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.

Tenuirostres

(Lat. tenuis, slender; rostrum, beak). A group of the Perching Birds characterised by their slender beaks.

Tergum

(Lat. for back). The dorsal arc of the somite of an Arthropod.

Terricola

(Lat. terra, earth; and colo, I inhabit). Employed occasionally to designate the Earth-worms (Lumbricidoe).

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.

Testis

(Lat. testis, the testicle). The organ in the male animal which produces the generative fluid or semen.

Tetrabranchiata

(Gr. tetra, four; bragchia, gill). The order of Cephalopoda characterised by the possession of four gills.

Thalassicollida

(Gr. thalassa, sea: kolla, glue). A division of Protozoa.

Theca

(Gr. theke, a sheath. A sheath or receptacle.

Thecosomata

(Gr. theke; and soma, body). A division of Pteropodous Molluscs, in which the body is protected by an external shell.

Theriomorpha

(Gr. ther, beast; morphe, shape). Applied by Owen to the order of the Tail-less Amphibians (Anoura).

Thorax

(Gr. a breastplate). The chest.

Thread-cells

(See Cnidae.)

Thysanura

(Gr. thusanoi, fringes; and oura, tail). An order of Apterous Insects.

Tibia

(Lat. a flute). The shin-bone, being the innermost of the two bones of the leg, and corresponding with the radius in the anterior extremity.

Totipalmatae

(Lat. totus, whole; palma, the palm of the hand). A group of Wading Birds in which the hallux is united to the other toes by membrane, so that the feet are completely webbed.

Toxodontia

(Gr. toxon, bow ; odous, tooth). A distinct order of Mammals.

Trachea

(Gr. tracheia, the rough windpipe), The tube which conveys air to the lungs in the air-breathing Vertebrates.

Tracheae

The breathing-tubes of Insects and other Articulate animals.

Trachearia

The division of Arachnida which breathe by means of tracheae.

Trematoda

(Gr. trema, a pore). An order of Scolecida.

Trichocysts

(Gr. thrix, hair; and kustis, a cyst). Peculiar cells found in certain Infusoria, and very nearly identical with the "thread-cells" of Coelenterata.

Trilobita

(Gr. treis, three; lobos, a lobe). An extinct order of Crustaceans.

Tritozooid

(Gr. tritos, third; zoon, animal; and eidos, form). The zooid produced by a deuterozooid ; that is to say, a zooid of the third generation.