APPENDIX. 



The unexpected nature of the facts brought forward in the preceding Memoir by its able 

 author rendered it necessary that some changes should be made in the classification of the birds 

 under consideration, or that the definitions of the families and orders should be modified accordingly. 

 The researches of Nitzsch and his contemporaries had made it evident that the muscular organ of 

 voice is present in all the Passeres up till their time examined. Its existence was therefore in- 

 corporated in the definition of the order. When Johannes Midler discovered that in many American 

 genera previously included in the order — although their voice organs had not been examined — 

 the vocal lower larynx is deficient, he assumed that the converse proposition was as true as that 

 which states that all oscine birds are passerine. Subsequent ornithological investigation, however, 

 has not substantiated the Miillerian dogma that all passerine birds are oscine, and the view 

 which now receives almost universal acceptance is that the single order Passeres is composed 

 of sub-orders and families, which, notwithstanding the differences in their larynges, are related 

 among themselves too intimately for them to be separated by an ordinal difference. 



The reasons for this view will now be considered seriatim. They rest upon the nature of — 



I. The foot. In all Passeres the hallux is directed backwards, at the same time that digits 

 ii, iii, and iv turn forwards. Among allied birds this is the case only in the Bucerotidae, 

 Alcedinidae, Momotidae, Coliidae, Upupidae, Meropidae, Caprimulgidae, and Coraciidae. 



II. The pterylosis. It is only in the Trogonidae that the pterylosis is the same as in 

 the Passeres (vide Nitzsch's Pterylography). 



III. The colic caeca. There are two short and narrow caeca coli, smaller than in any of 

 the allied birds. Colic caeca are found also in the Trogonidae, Meropidae, Galbulidae, and 

 Coraciidae. 



IV. The vomer. The vomer is trancated in front, except in Menura superha, and runs 

 forward as far as the line joining the anterior extremities of the separate maxillo-palatines. In the 

 Capitonidae and Ramphastidae only among allied birds is the vomer truncated, but in them it 

 ceases behind the maxillo-palatines, which sometimes fuse across the middle line, sometimes 

 are free from one another. 



V. The sternum. A single notch on each side (sometimes, as in Heteralocha gouldi, converted 

 into a foramen) of the posterior margin of the sternum, divided into two in the Pteroptochidae, 

 is found in all Passeres, at the same time that the manubrium sterni is large and bifid (but slightly 

 so in Chihia and Eurylaermis). 



VI. The tensor patagii brevis muscle. In the triangular patagium of the wing of the bird 

 the tendons of two nmscles are to be found. One is that of the tensor palaffii lo7igus, which 

 forms the supporting cord of the free margin of the membrane itself. The second is that of 



