390 
DR. e. w. shufeldt’s morphological 
And this is the way, I suspect, that certain forms which we 
now see in our modern Swifts were differentiated from the early 
Hirundine stock. That this occurred early in the chapter of 
avian life-history, for the world is old, may be conjectured 
from the fact that Cypseli |are now quite cosmopolitan birds, 
and, moreover, have many representatives among them which 
present highly specialized organization. Even at the present 
time, however, ive yet have forms that structurally are nearer 
the Swallows than others of the same group. To instance this, 
yve have but to glance at two such birds as Micropus viela- 
noleucus aud Chcetura pelagica, in the first of which we still find 
the general Swallow-like form of the body, the average depth of 
the carina of the sternum, the non-pneumatic humerus, and other 
points, all of which are far more Cypseline in character in the 
latter bird. Clicctura , too, agreeing with other spine-tail Swifts, 
shows its greater fixedness of characters in the very structures 
which gives it its name, for the spines which terminate its rec- 
trices are useful to the bird, yet cau only have been developed 
through ages of time. When we come to examine the still more 
Swallow-like Swifts, Hemiprogne for example, and its allies, I am 
sure we shall meet with other points in their anatomy w'hich will 
lend support to this view of the origin of these types. 
In the present memoir I have, by extensive and careful com- 
parative investigations into structure, attempted to point out 
how entirely different these Swifts are from the Humming- 
birds, a group with which they have long been associated, to 
my mind upon very meagre claims. During the course of my 
present researches I have shown that Cypseli differ from 
Trochili, (1) in their habits ; (2) in their nidification ; (3) in 
the method of securing their food ; (4) in all their external 
characters, and markedly in their external form ; (5) in their 
pterylosis ; (0) fundamentally in their skeletons ; (7) every struc- 
ture in their heads is as widely at variance as an} r tw r o forms 
of birds in the Class ; (8) in their wing-structures ; (9) in their 
pelvic limbs ; (10) in their respiratory apparatus ; (11) in their 
visceral anatomy ; and (12) in their digestive system. These 
two groups have been associated together upon an entirely false 
system of classification, which assumed first, that they are alike 
in their wing-structure — a resemblance which I have shown to 
be purely superficial ; secondly, that they both have an unuotched 
sternum, although physiological law demands it, and when asso- 
ciated with an entire organization that widely differs from that 
