ORDER II . 



INSESSORES; 



la accordance with the views of many systematic writers, it may perhaps he as well. to retain 

 an order Insessores, and to place in it the Strisores, Clamatores, and Oscines as sub-orders. The 

 characters of the order will then consist chiefly in the possession of three toes in front and one 

 behind, (or at least never with two toes directed backwards,) as in Scansores. The claws are 

 not retractile, nor the bill with a cere, as in the Baptores ; nor is the hind toe situated appreci- 

 ably above the plane of the others, as in Rasores, Grallatores, and Natatores. 



The hind toe of the Insessores corresponds to the thumb or inner toe of the mammals, and is 

 usually quite short. The joints of the anterior toes generally follow the law of number charac- 

 teristic of birds, namely, two to the hinder, three to the inner, four to the middle, and five to 

 the outer toes ; but a deviation is seen in some Strisores where there are sometimes but three 

 joints each to the anterior toes, and sometimes only four in the outer. The tarsi are generally 

 covered anteriorly with plates, and furnished behind with granulations or small scales, or else 

 with two long plates covering the sides, the latter feature especially characteristic of the 

 Oscines, or singing birds ; in the latter alone is the tarsus sometimes covered anteriorly with 

 a single plate. Sometimes the tarsus is entirely or partly naked, or destitute of plates altogether. 



The carpal joint or the hand part of the wing is in most Insessores furnished with ten quills^ 

 (primaries,) although the first quill is sometimes very short or even entirely wanting, as in 

 many Oscines. The fore arm has from six (in the humming birds) to thirteen quills, the 

 average being eight or nine. 



There are certain peculiarities in the arrangement of the wing coverts of the different sub- 

 orders of Insessores, constituting important distinctive features. Some of these will be hereafter 

 referred to. 



The tail of the Insessores exhibits considerable difierences. The number of feathers is usually 

 twelve ; sometimes ten only, as in the Strisores. 



The different groups of the order Insessores are subject to considerable variations in respect to 

 the structure of the lower larynx attached to the trachea or wind pipe just anterior to its division 

 into the two bronchial tubes. Cuvier long since showed that the true singing birds had the 

 larynx provided with a peculiar apparatus for the purpose of effecting a modulation of the 

 voice, composed of five pairs of muscles, of which other birds were destitute in greater part 

 or entirely. The characteristic of the groups Strisores, Clamatores, and Oscines, and of their 

 sub-divisions, as will be shown hereafter, depend very much on these peculiarities of the larynx. 



The tongue of the Insessores varies to a considerable degree. In the humming birds it is 

 thread-like and bifurcated. In most other insessorial or perching birds it is long or short, flat, 



' Tho following remarks on the general characters of the Insessores are derived chiefly from Burmeister'sThiere Brasiliens, 

 Vogel, page 305. 



