ZOONAVA. 
characteristic, as is also the wing-formation, the primaries being very long 
and narrow and rapidly decreasing, while the secondaries are very short, 
being exceeded by the shortest primary. The tail is square, or more or less 
forked, generally short ; in some cases the shafts of the tail-feathers are soft 
and normal, in others the shafts are stiffened and the tips project bejrond the 
webbing as needle-points. The legs show further differences : the toes are 
always four in number, but sometimes they are feathered, sometimes normal 
and naked ; the tarsus is sometimes feathered, sometimes not, but when it is 
naked it generally shows neither scutes nor reticulations, but is complete and 
sldn-like. The toes are diversely placed ; sometimes all four toes point 
forward, sometimes two forward and two backward, and others normal, the 
hind toe alone pointing backward. 
These differences have been used for the separation of the group into 
sections, but I do not consider them in that connection. It is certain that 
osteological results will show that such sections are useless. In this connection 
I might quote a statement regarding the diastataxy and eutaxy of the wing. 
Very few groups show both these conditions and the Swifts are one. Delbitt 
Miller {Bull. Amer. Mus. Nat. Hist., Vol. XXXIV., 1915, p. 132) wrote : 
“ Groups containing both Eutaxic and Diastataxic forms, Cypseli (Swifts). 
Mostty eutaxic. Streptoprocne and Collocalia said to be diastataxic. Dendro- 
chelidonidce (aU ?) diastataxic.” 
It is noteworthy to find Collocalia and Streptoprocne together, because 
these are probably the most different superficially of all the genera of the group. 
If this statement be true, it suggests at once that little relationship (direct) 
can be considered to exist between these two and that the condition has 
independently evolved in these two genera. 
Grey rump 
No grey rump . . 
Key to the Species. 
Z. francica, p. 248. 
Z. fuciphaga, p. 255. 
247 
