Trochal

(Gr. trochos, a wheel). Wheel-shaped ; applied to the ciliated disc of the Rotifera.

Trochanter

(Gr. trecho, I turn). A process of the upper part of the thighbone (femur) to which are attached the muscles which rotate the limb. There may be two, or even three, trochanters present.

Trochoid

(Gr. trochos, a wheel; and eidos, form). Conical with a flat base ; applied to the shells of Foraminifera and Univalve Molluscs.

Trophi

(Gr. trophos, a nourisher). The parts of the mouths in insects which are concerned in the acquisition and preparation of food. Often called "instrumenta cibaria."

Trophosome

(Gr. trepho, I nourish; and soma, body). Applied collectively to the assemblage of the nutritive zooids of any Hyarozoon.

Truncated

(Lat. trunco, I shorten). Abruptly cut off; applied to univalve shells, the apex of which breaks off, so that the shell becomes "decollated."

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."

Turbellaria

(Lat. turbo, I disturb). An order of Scolecida.

Turbinated

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

Ulna

(Gr. olene, the elbow). The outermost of the two bones of the fore-arm, corresponding with the fibula of the hind-limb.

Umbellate

(Lat. umbella, a parasol). Forming an umbel - i.e., a number of nearly equal radii all proceeding from one point.

Umbilicus

(Lat. for navel). The aperture seen at the base of the axis of certain univalve shells, which are then said to be "perforated" or " urnbilicated."

Umbo

(Lat. the boss of a shield). The beak of a bivalve shell.

Umbrella

The contractile disc of one of the Lucernarida.

Uncinate

(Lat. uncinus, a hook). Provided with hooks or bent spines.

Unguiculate

(Lat. unguis, nail). Furnished with claws.

Ungulata

(Lat. ungula, hoof). The order of Mammals comprising the Hoofed Quadrupeds.

Ungulate

Furnished with expanded nails constituting hoofs.

Unilocular

(Lat. units, one; and loculus, a little purse). Possessing a single cavity or chamber. Applied to the shells of Foraminifera and Mollusca.

Univalve

(Lat. unus, one; valvae, folding doors). A shell composed of a single piece or valve.

Urodela

(Gr. oura, tail; delos, visible). The order of the tailed Amphibians (Newts, etc.)

Urticating Cells

(Lat. urtica, a nettle). (See Cnidae).

Vacuoles

(Lat. vacuus, empty). The little cavities formed in the interior of many of the Protozoa by the presence of little particles of food, usually surrounded by a little water. These are properly called " food vacuoles," and were supposed to be stomachs by Ehrenberg. Also the clear spaces which are often seen in the tissues of many Coelenterata.