Jeffries on the Primaries of Birds. 
1 63 
If we summarize the above facts we find that the number of 
primaries of which signs can be found varies from ten to eleven 
in Carinate birds, while many more exist in the JR.atitate birds, 
while the functional primaries vary from nine to eleven in number. 
In regard to the primary coverts, there are for the most part one 
less than the number of primaries, varying from nine to ten in 
number. All the above conditions can be classed in four groups, 
the first group containing the nine primaried birds, all of which 
belong to the Oscines. In this group the first primary and the 
first covert are rudimentary. The second group, containing all 
birds with ten developed primaries and nine coverts, includes the 
rest of the Oscines , and Pici , and I presume most of the other 
Passerine groups. 
The third group, all those with ten primaries and ten coverts, 
includes the Cypseli , Pro chili. Ardeidce , Purbinares , and prob- 
ably others, the young of which I have not been able to examine. 
The last group, containing those birds with eleven primaries, 
includes the Alcedinidce , Palconidce , Plotidce , Ciconiidce , Phoe- 
nicopteridce , Anatidce , Charadriidce , Scolopacidce , Paridce , 
Coly?nbidce , Aicidce , and probably most of the other lower birds. 
Thus we see that the number of primaries does not hold con- 
stant for the larger groups of birds, but that the higher birds of 
the various groups show a tendency towards a reduction in the 
number of primaries. So the reduced number of primaries and 
coverts would seem to point to high development, but not to be 
of use in dividing the major groups. 
The rule according to which the primaries and coverts abort 
is interesting and of importance, since it makes it possible to 
decide whether a u little feather” be a primary or a covert. The 
law is simply that the most distal one aborts first, hence a covert 
before its primary. Hence when one ‘‘little feather” is found 
we can tell if it be a covert, as in the Pyrannidce , or a primary, as 
in the Kingfishers, by seeing what the next developed feather 
is, — in the first case a primary, in the last a covert. When there 
are two little feathers one is a primary and the other a covert, the 
covert being uppermost. 
The definiteness in the wing formula of birds closely related is 
very great, the formula for one answering perfectly for the rest. 
So the plan ought to be a help in determining the position of 
doubtful birds. 
