TECHNICAL TERMS. 35 



last-mentioned Birds afford the greatest assistance in springing 

 into the air. 



10. The vent feathers and under-tail coverts, that extend from 

 the anus or vent to the tail underneath. These feathers are 

 much longer in some tribes of Birds than others. Those that 

 have a constant habit of flirting up their tails — like, for example, 

 the Eallus Carolinus, and several species of small shore Birds — 

 have the vent feathers unusually well developed. 



The tail feathers are various in size and numbers, and are 

 generally the most ornamental part of a Bird. The tail per- 

 forms the most necessary office in the navigation of the Bird 

 through the air ; in fact, it is the rudder by which the coarse of 

 the Bird is determined, and acts in concert with the will of the 

 Bird as freely as a ship obeys her helm. 



11. Loral space. — The space between the bill and eye. 



12. Frons. — The forehead. 



13. Corona. — Crown of the head. 



14. Occiput. — The hind part of the head. 



15. Flexure. — Bend of the wing. 



16. Tarsi. — Shanks of the legs. 



17. r^■5^■a.— Thigh. 



The upper and lower bills are called the superior and inferior 

 maxilla., or upper and lower mandibles. 



Iris — irides. — The colored circle surrounding the pupil of the 

 eye. 



Mentum. — The chin. 



Guttur. — The throat. 



Collum. — The neck. 



Pectus. — The breast. 



In measurement, the total length means from point of bill to 

 the end of middle tail feathers. Length of the wings means 

 from the bend of the wing to the end of the longest quill 

 feather. 



