GLOSSARY. 5 



Alve'olns (L. alveolus, a little hollow). A small depression ; 

 the socket of a tooth. Also the name given to each of the 

 five pieces of which the oral skeleton is composed in the 

 Echinidea. The ultimate saccules of a racemose gland. 



Ambula'cra (L. ambulacrum, a garden walk). The spaces in 

 the tests of sea-urchins and star-fishes, containing the 

 apertures through which the " tube feet " are protruded. 



Ambnla'cral. Relating to the ambulacra, as the ambulacral 

 vessels. 



Ambula'cral ossicles (L. ambulacrum, a garden walk ; ossiculum, 

 a little bone). In the star-fishes, the ossicles which bound 

 the sides and roof of the ambulacral grooves. 



Am'bulatory (L. ambuldre, to walk). Applied to the appen- 

 dages of Crustacea which are used in walking. 



Ameta'bola (Gr. a, not; metabole, change). The insects which 

 do not undergo metamorphosis. 



Ami'adae. A sub-order of Ganoid fishes. 



Am'monite (so called from their resembling the horns on the sta- 

 tues of Jupiter- Ammon). A group of extinct Cephalopods. 



Am'nion (Gr. amnos, a lamb). One of the appendages of the 

 foetus in mammals and birds. 



Amoe'ba (Gr. ameibo, I change). A genus of the Rhizopoda, 

 the members of which constantly change their shape. - 



Amce'boid (Gr. ameibo, I change). Like an amoeba. 



Amphiarthro'sis (Gr. amphi, both ; arthron, an articulation). 

 An articulation of bones partaking of the character both 

 of a diarthrosis or moveable joint, and a synarthrosis or 

 immoveable joint. 



Amphibia (Gr. amphi, both; bios, life). A division of the 

 Vertebrata adapted for breathing in water when young, 

 and in air when mature. 



Ampblcce'lus (Gr. amphi, both; koilos, hollow). Applied to 

 vertebrae which are concave at both ends. 



Amphidiarthro'sis (Gr. amphi, both; diarthrosis, an articulation). 

 A term applied to such an articulation as that of the 

 lower jaw with the temporal bone, because it partakes of 

 the nature of a hinge-joint, and, at the same time, admits 

 of a movement from side to side. 



Amphidis'cus (Gr. amphi, both ; diskos, a disc or quoit). A 

 siliceous body resembling two cogged wheels connected 

 by an axle, found in some sponges. 



Amphimor'phae (Gr. amphi, both ; morphe, form). A group of 

 birds which comprises the flamingoes. 



