146 ELEMENTS OF ORNITHOLOGY, 
and is called the culmen. The lower line coincides with its 
lowest margin, that which encloses the under mandible. This 
lower line is the mawillary tomium. The culmen may be in the 
form of a sharp elevated ridge like a knife, when it is said to 
be “ cultrate,” the mandible which bears it being “keeled”; the 
apex of the upper mandible may be hamulate or unguiculate. 
The maxillary tomium may bear tooth-like processes or be 
notched like a saw, when it is said to be serrate. If it has a 

Parts or A Bru. 
a, Side of maxilla or upper mandible ; 2, culmen ; ¢, nasal fossa; d, nostril ; 
e, tomia or inferior margin of upper mandible; /, gape, or whole com- 
missural line; g, rictus; 2, commissural point or angle of the mouth ; 
i, ramus of under jaw; 7, tomia of under mandible ; /, angle of gonys: 
the hindermost pomt of junction of the two rami which form the lower 
mandible is the ‘gonys proper,” but the term is extended to apply to 
the whole line of union of the rami from the gonys proper to the tip 
of the under mandible corresponding to the culmen or median ridge 
and upper outline of the upper mandible; 7, 7, side of under mandible ; 
n, tips of mandibles. 
single notch or tooth-like process (as in the Hawk) it is called 
dentate. If it forms a sharp edge like that of a knife it is 
(like a sharp culmen) termed cultrate, and if it is at the same 
{ime much curved it is falcate, or “like a sickle.’ An upper 
mandible provided with a series of transverse plates or ridges 
within it (like that of the Duck) is called lamellate. 
The nostrils are almost always conspicuous one on either 
side of the upper mandible. Asa rule they each open at the 
bottom of a depression, which when rounded is termed the 
