=The Affinities of= _Chamæthlypis_.—As generic distinctions become more and more refined the need of a supergeneric group intermediate between the family or subfamily and the genus, corresponding approximately to the former genus, becomes increasingly evident.
In his great work on the ‘Birds of North and Middle America’ Mr. Ridgway has supplied this want in many families. In the Warblers (Mniotiltidæ) the grouping does not appear to be so successful as in most cases. Not only is the old genus _Geothlypis_ broken up into three genera but these are distributed in as many supergeneric groups. _Oporornis_ is banded with _Dendroica_ and its allies in the Dendroicæ, while _Chamæthlypis_ is placed in the Icteriæ.
We cannot help feeling that this arrangement is artificial, and that too much importance has been placed on the length of the wing-tip (easily modified by habits and migration), and insufficient weight given to coloration, nesting and even song.
Also, the distinctions are partially invalidated by exceptions. Thus the sections including _Geothlypis_ and _Chamæthlypis_ are separated by differences in the length of the tail and form of the bill; but _Geothlypis nelsoni_ agrees with _Chamæthlypis_ in having the tail longer than the wing. Again the Geothlypeæ are separated from the Dendroiceæ by having the rictal bristles obsolete and the wing-tip shorter, but in _Geothlypis æquinoctialis_ and _G. cucullata_, at least, the rictal bristles are well-developed.
The particular point of criticism is in regard to the affinities of _Chamæthlypis_ which is distinguished from _Geothlypis_ by its stouter bill, with strongly curved culmen, and its longer, graduated tail.
Mr. Ridgway expresses the opinion that while “this genus is very much like _Geothlypis_ as to its general appearance” it is “quite distinct structurally, in which respect it comes much nearer to _Icteria_.” I have carefully tabulated the structural differences between these three genera, and the result to my mind unquestionably indicates a nearer relationship of _Chamæthlypis_ with _Geothlypis_.
Sharpe (Hand-List of Birds) while recognizing _Chamæthlypis_, included in this genus two South American species of _Geothlypis_, _G. æquinoctialis_ and _G. auricularis_. These two species and _G. cucullata_ are intermediate between _Chamæthlypis_ and the typical species of _Geothlypis_ in coloration and in the form of the bill and have well developed rictal bristles as in _Chamæthlypis_. They do not, however, approach the latter genus in the length of the tail, as do certain Mexican species of _Geothlypis_, notably _G. nelsoni_.