is_, a tower). A genus of the _Ammonitidoe_.

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

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. _unus_, one; and _loculus_. a little purse).
Possessing a single cavity or chamber. Applied to the shells
of _Foraminifera_ and _Mollusca_.

UNIVALVE (Lat. _unus_, one; _valvoe_, folding-doors). A shell
composed of a single piece or valve.

URODELA (Gr. _oura_, tail; _delos_, visible). The order of the
Tailed Amphibians (Newts, &c.)

VENTRAL (Lat. _venter_, the stomach). Relating to the inferior
surface of the body.

VENTRICULITES (Lat. _ventriculum_, a little stomach). A genus
of siliceous Sponges.

VERMIFORM (Lat. _vermis_, worm; and _forma_, form). Worm-like.

VERTEBRA (Lat. _verto_, I turn). One of the bony segments of the
vertebral column or backbone.

VERTEBRATA (Lat. _vertebra_, a bone of the back, from _vertere_,
to turn). The division of the Animal Kingdom roughly characterised
by the possession of a backbone.

VESICLE (Lat. _vesica_, a bladder). A little sac or cyst.

WHORL. The spiral turn of a univalve shell.

XIPHOSURA (Gr. _xiphos_, a sworn; and _oura_, tail). An order of
_Crustacea_, comprising the _Limuli_ or King-Crabs, characterised
by their long sword-like tails.

XYLOBIUS (Gr. _xulon_, wood; _bios_, life). An extinct genus of
Myriapods, named in allusion to the fact that the animal lived
on decaying wood.

ZAPHRENTIS (proper name). A genus of Rugose Corals.

ZEUGLODONTIDAE. (Gr. _zeugle_, a yoke; _odous_, a tooth). An extinct
family of Cetaceans, in which the molar teeth are two-fanged,
and look as if composed of two parts united by a neck.

ZOOPHYTE (Gr. _zooen_, animal; _phuton_, plant). Loosely applied
to many plant-like animals, such as Sponges, Corals, Sea-anemones,
Sea-mats, &c.

INDEX.

Acadian Group.
_Acer_.
_Acervularia_.
_Acidaspis_.
Acorn-shells.
_Acroculia_.
_Acrodus; nobilis_.
_Acrotreta_.
_Acroura_.
_Actinocrinus_.
_AEglina_.
_AEpiornis_.
_Agnostus; rex_.
_Alces malchis_.
_Alecto_.
_Alethopteris_.
_Algoe_ (_see_ Sea-weeds).
Alligators.
_Alnus_.
_Amblypterus; macropterus_.
_Ambonychia_.
_Ammonites; Humpresianus; bifrons_.
_Ammonitidoe_.
_Amphibia_; of the Carboniferous; of the Permian; of the Trias;