10 Ridgway — American Families of Oligomi/odian Passeres. 



c. Nares liolorhiiial or modified schizoiliinal ; palate scliizognathous ; 



outer toe much shorter than middle toe (not conspicuously longer 



than inner toe), the three anterior toes coherent for much less 



than full length of their basal phalanges. 13. Furnariidae. 



cc. Nares holorhinal ; palate aegithognathous or senii-desmognathous ; 



outer toe nearly (sometimes quite) as long as middle toe, both 



conspicuously longer than inner toe, the three anterior toes 



coherent (fused) for entire length of their basal phalanges. 



14. Dendrocolaptidae. 



It should be stated here that the Tracheophonae have not yet 

 been critically studied by me and that the above scheme is 

 purely eclectic. It may 1)6 that when these are taken in hand a 

 similar nonconformity of the character of the tarsal envelope to 

 Dr. Sclater's keys may be discovered as in the case of the Co- 

 tingidse. The same remarks apply in part to the Oligomyodian 

 family Pittidse. 



So few of the INIesomyodian forms have been studied as to 

 their internal structure that I feel sure a satisfactory increase of 

 our knowledge in this respect will result in more or less funda- 

 mental modification of our present views as to their classifica- 

 tion. The anachromyodous syrinx and homoeomerous thigh- 

 artery of many genera of Tyrannidte as well as the catacromyo- 

 dous syrinx and heteromerous thigh of many forms of PipridjB 

 and Cotingidse are, for example, merely assumed, and there 

 may be many exceptions to these supposedly diagnostic charac- 

 ters of the groups in question. So far as external characters are 

 concerned, certainly some genera commonly referred to the 

 Cotingidae can be separated from the Tyrannidae only by their 

 non-cxaspidean tarsal envelope, and at the same time certain 

 genera commonly referred to the Tyrannidae also have the tarsal 

 envelope non-exaspidean. In the group called Cotingidae the 

 character of the tarsal envelope is exceedingly variable, and the 

 homogeneity of the group is open to very serious doubt. Of all 

 external characters, to which present recourse is necessarily 

 limited, the character of the tarsal envelope is by far the most 

 nearly diagnostic, for the Oligomyodi may be sharply divided 

 into two major groups, one of which, comprising Oxyruncidae, 

 Tyrannidae (as here defined) and Pipridae, having the tarsus 

 exaspidean, the other, comprising Cotingidae, Rupicolidae, 

 and Phytotomidae, among American forms, having the tarsus 



