378 Clark, The Classification of Birds. \J^^ 



COLUMBIFORM, 



Upper cervical tract wide, strongly forked between shoulders, often 

 united with lower cervical, until near the shoulders. 



Dprsal tract very broad and diffuse, fairly separable from cervical, but 

 inseparable froni femorals. 



Humeral tracts very broad and strong. 



Femoral tracts large, not distinct from dorsal. 



Lower cervical tract slightly or not at all forked, continuous with the 

 sternals. 



Sternals broad, completely united with the ventrals. 



\'entrals broad, not widely separated, l^ut not united posteriorly. 



This type is clearly shown by the Pigeons and Sand Grouse. 



Passeriform. 



Upper cervical tract narrow, well-defined, and continuous with the 

 dorsal tract. 



Dorsal tract not clearly distinguished from the cervical, more or less 

 widened (often enclosing a prominent apterium), generally narrowed 

 as it approaclies the tail. The dorsal tract is frequently distinctly 

 divided into two parts, the anterior of which is usually forked ; less 

 commonly the posterior part is forked. 



Humeral tracts moderate, frequently nariow. 



Femoral tracts usually weak and small, sometimes wholly wanting, and 

 sometimes quite clearly defined. 



Lower cervical tract more or less forked. 



Sternals usually strong and well-marked. 



Ventrals rather narrow, widely separated on belly, and not reaching 

 the anus ; usually not separated from sternals, but sometimes partly- 

 distinct. 



This type is shown to a greater or less degree by all those 

 birds, usually classed as Cuculiformes, Coraciiformes and Passeri- 

 formes. Its varieties are fairly constant and may assist in the 

 arrangement of these groups in suborders and families. 



The following table will help to make the character of the ten 

 types more easily grasped, but it must be borne in mind that this 

 arrangement is very artificial and is in no sense a ' Key.' 



