20 EXTERNAL PARTS 



brane ' extending over the nostrils, is found in the doves and 

 in the pigeons. The rictal portion of the mouth is frequently- 

 fringed with longer or shorter hairs ; these are called rictal 

 bristles} 



Shape of the gape. — The gape is straight ^ when the commis- 

 sural line, formed by the tomia and the rictus, is straight. 

 This line may be curved,'^ sinuate* or ungulate.^ 



General size and form of the bill. — The length of the head is 

 used to measure the length of the bill. A long " bill is longer 

 than the head, a short ^ bill shorter, and one of medium length 

 is about as long as the head. A compressed^ bill is one flat- 

 tened sideways, so that its height is greater than its width. A 

 depressed ^ one is flattened up and down, or is wider than high. 

 A straight '"' bill is not only straight throughout its length, but 

 is also in line with the head. If not in line with the head, it 

 is said to be bent}^ A recurved " bill is one that curves upward, 

 and a decurved^^ bill one that curves downward. A bill may 

 be decurved throughout, or it may have merely a dec%irved tip}* 



The usual bill is sharp-pointed at the end and is called 

 acute}' If it has an abrupt and somewhat rounded end, it is 

 obtuse}^ Acuminate " indicates not only an acute end, but a 

 slender bill as well. If very slender and sharp, it is called at- 

 temtate}^ In some cases, as among the hummingbirds, still 

 more emphatic words are needed to denote slenderness and 

 sharpness. Subulate'^^ is more emphatic than attenuate, and 

 acicular indicates the extreme limit in this direction. 



