176 Proceedings of the Royal Physical Society. 
characteristics of its palatal structure, of its myology, of its 
visceral anatomy, or of its pterylosis. Like all other single 
characters, however, this particular one has less taxonomic 
value in certain cases than in others; but its claim to rank 
as a taxonomic feature of some importance now hardly admits 
of being called in question. The Medians and also the Minors 
participate in the faulting that accompanies aquincubitalism. 
At first it appeared as if the variations in the style of wing 
coverts arising from the absence of the 5th cr. might be 
trusted as a feature of taxonomic value, and in my earlier 
papers it was so treated. But recent investigations by Dr 
Sclater and others have shown that this view of its import- 
ance cannot be sustained. Whole groups of birds are, it is 
true, characterised by the “faulted” coverts, which mark the 
absence of the 5th cr. It may be said, indeed, that the 
Euornithes may be divided into three sections, in accordance 
with this feature. The whole of the Trochili, Passeres, 
Coccyges, Crypturi, Hemipodes, and Galline are characterised 
by the unfaulted cubital coverts which mark the quincubital 
birds. In the whole of another large group, comprising the 
Caprimulgi, Psittaci, Striges, Accipitres, Catharte, Ser- 
pentarii, Pandiones, Pernidse, Herodiones, Anseres, Columbe, 
Steganopodes, Tubinares, all the Gavio-gralle (except one 
genus of Fulicariz), including the Cranes, the Bustards, and 
the Sandgrouse, have the wing coverts faulted. On the other 
hand, while in the majority of the Pici, Coccyges, and Cypseli 
the wing coverts are unfaulted—the 5th cr. being present— 
yet in many species of Picarian birds and Swifts, about whose 
close relationship to the normal forms there can be no doubt, 
the 5th cr. is absent, and the coverts are faulted accordingly. 
Closely allied genera of Swifts as well as of Kingfishers may 
show these exceptional characteristics. . 
The one feature of this kind that does appear to be con- 
stant in allied groups of birds is the direction of overlap of 
the first twelve Medians and their accompanying Minors. 
In the Trochili, Trogones, Paradisiide, Coccyges, Muso- 
phagide, Caprimulgi, and some few other forms, the whole 
of the wing coverts—majors, medians, minors, and marginals 
—overlap distally. On the first five of these the 5th cr. is 
