30 Accotint of Observed Forms of Larynx. 



and the pessulus. The lateral muscles of the trachea, and the musculi sternotracheal^ are 

 of the ordinary form. 



A genus allied to this has been discovered, which also stands very close to 

 it in regard to the larynx — the genus Orchilns Cab. [Toclus megacephalns Sw.) The 

 five lowest rings of the trachea are cleft behind, and contain in this cleft a small 

 bony clasp, which is a continuation of the pessulus. The laryngeal muscle resembles that 

 of Colopterus in direction, and is inserted into the hinder part of the fourth half-ring. 

 The azygos muscle of the trachea, found in Colojoterus, is wanting. 



Another genus of the Todbiae, Todirostrum Less. {Triccus Cab.) wants the cleft. It 

 has no large laryngeal muscle, but the lateral muscle of the trachea is simply continued 

 to the bronchus, and raises the fourth half-ring, as in Mi/iolius and Ariindinicola. The 

 cartilago ayrtaenoidea is wanting ; the branches of the trachea resemble those of the rest 

 of the Todinae. I have examined Todirostrum cinereum Less. [Todits cinereus L.) and Triccus 

 poliocephalus Cab. [Todiis jjoUocephalus Pr. M.) 



These four species of the Todinae examined by me possess only a single notch in 

 the sternum. The type of the true genus Todus, T. viridis L. has two notches on each 

 side. The trachea is perfect; I cannot say how the tracheal muscle is situated, on 

 account of the imperfect state of the birds examined. 



(vi.) Organ of Voice of the Myiotherinae, Scytalopinae, Anabatinae, 



and Dendrocolcqytinae. 



In most birds the organ of voice is formed by the end of the trachea and the 

 beginning of the bronchi. In some it is altogether bronchial, as is the case in Steatornis 

 and CrotopJiaga. In S. caripensis the bronchi preserve, for a long distance, the perfect 

 rings of the trachea, so that there are from eleven to sixteen perfect bronchial rings ; the 

 next ring is very strong and no longer perfect, the following half-ring is still thicker, and 

 is acted on by the vocal muscle. In C. major there are eight perfect bronchial rings, and 

 the muscle is inserted into the tenth. 



A division of the Passerines, which is partly placed under the Shrikes, partly under 

 the Thrushes, partly under the Fly-catchers, and partly under the Wrens, is distinct 

 among birds from the peculiarity, till now unknown, that the organ of voice is formed 

 by the lower larynx alone without the aid of the bronchi ; and this offers a perfectly 

 aberrant form of structure. This portion of the trachea is flattened from before back- 

 wards, its walls are thin and membranous, and consists of extremely fine anterior 

 and posterior half-rings, which are fastened to the sides by long elastic bands. The 



