GLOSSARY OF TECHNICAL TERMS. 



A. 



Abdomen. Belly. 



Aberrant. Deviating from ordinary character. 



Abortive. Remaining or becoming imperfect, 



Actinosts. A series of bones at the base of the pectoral rays. 



Acuminate. Tapering gradually to a point. 



Acute. Sharp-pointed. 



Adipose fin. A peculiar fleshy fin-like projection behind the dorsal fin, on 



the backs of salmons, catfishes, etc. 

 Adult. A mature animal. 



/Egithognathus. Having the peculiar palate of passerine birds. 

 Air-bladder. A sac filled with air, lying beneath the backbone of fishes, 



corresponding to the lungs of the higher vertebrates. 

 Albinism. State of whiteness, complete or partial, arising from deficiency 



or entire lack of pigment in the skin and its appendages. 

 Alisphenoid. A small bone on the anterior wall of the brain-case. 

 Allantois. An organ of the embryo. 

 Altrices. Birds hatched in an immature condition, reared in the nest and 



fed by the parents. 



Altricial. Having the nature of altrices. 

 Alula. Literally, little wing. The feathers attached to the so-called 



"thumb" of a bird. 

 Alveolar surface. A portion of the jaw of a Turtle, where the teeth sockets 



are developed in other reptiles. 

 Amnion. An organ of the embryo. 

 Amphicoelian. Double-concave, said of vertebrae. 

 Anadromous. Running up .-said of marine fishes which run up rivers to 



spawn. 



Anal. Pertaining to the anus or vent. 



Anal fin. The fin on the median line behind the vent on fishes. 

 Anal plate. The plate immediately in front of the vent on serpents, often 



divided in two by a median suture. 

 Anchylosed. Grown firmly together. 



Angular. A small bone on the posterior end of the mandible. 

 Anteorbital plate. The plate (one or two) in front of the eye in serpents, 



with its longest diameter vertical ; also called preocular. 

 Antrorse. Turned forward. 



Anus. The external opening of the intestine ; the vent. 

 Arboreal. Living in trees. 

 Arterial bulb. The muscular swelling at the base of the great artery, in 



fishes. 



[106] 



