. Birds: the elements of ornithology . ll be angulate when both the tomia and the rictus are nearlystraight but do not lie in one line, and, therefore, form an angleat their point of junction, The maxilla or upper mandible has two definite lines mostevident to the observer when the bill is viewed in profile. Oneof these lines coincides with the uppermost margin of the bill * See p. See above, p. 30. J This distinction was proposed by Elliott Coues in the second edition ofhis Key to North American Birds, p. 105. Ii 146 ELEMENTS OF OEFITHOLOGX. and is called the culmen. The lower line coin
. Birds: the elements of ornithology . ll be angulate when both the tomia and the rictus are nearlystraight but do not lie in one line, and, therefore, form an angleat their point of junction, The maxilla or upper mandible has two definite lines mostevident to the observer when the bill is viewed in profile. Oneof these lines coincides with the uppermost margin of the bill * See p. See above, p. 30. J This distinction was proposed by Elliott Coues in the second edition ofhis Key to North American Birds, p. 105. Ii 146 ELEMENTS OF OEFITHOLOGX. and is called the culmen. The lower line coincides with itslowest margin, that which encloses the under mandible. Thislower line is the maxillary tomium. The culmea may be in theform of a sharp elevated ridge like a knife, when it is said tobe oultrate the mandible which bears it being heeled; theapex of the upper mandible may be hamulate or maxillary tomium may bear tooth-like processes or benotched like a saw, when it is said to be serrate. If it has a Kg. J Paetsof a Bill. , Side of maxilla or upper mandible ; b, culmen; c, nasal fossa; d, nostril;e, tomia or inferior margin of upper mandible; /, gape, or whole com-missural line; a, rictus; h, commiasural point or angle of the mouth;i, ramus of under jaw; 7, tomia of under mandible ; i, angle of gonys:the hindermost point of junction of the two rami which form the lowermandible is the gonys proper, but the term is extended to apply tothe -whole line of union of the rami from the gonys proper to the tipof the under mandible corresponding to the culmen or median ridgeand upper outline of the uppe^ mandible; I, m, side of under mandible;n, tips of mandibles. single notch or tooth-like process (as in the Hawk) it is calleddentate. If it forms a sharp edge like that of a knife it is(like a sharp culmen) termed cultrqte, and if it is at the sametime much curved it is falcate, or like a sickle. An uppermandible provided with a series of transverse plates
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