696 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
Genus STREPTOPROCNE Oberholser. 
Streptoprocne ¢ OBERHOLSER, Proc. Biol. Soc. Wash., xix, May 1, 1906, 69, in text. 
(Type, Hirundo zonaris Shaw.) 
Very large Cheturine Swifts (wing 180-235 mm.) with the hallux 
more than half as long as inner toe, tarsus longer than middle toe 
with claw, lateral toes scarcely shorter than middle toe, shafts of 
rectrices very rigid and more or less produced terminally, the colora- 
tion plain blackish or sooty with a white collar, at least across 
hindneck. 
Nostrils elliptical, nearly parallel, for the greater part (some- 
times wholly) anterior to the latero-frontal antia; distance from 
tips of longest secondaries to that of longest primary a little less than 
two-thirds the total length of wing; tenth (outermost) primary 
longest; tail about one-third as long as wing, emarginate (S. zonaris) 
or truncate (S. semicollaris), the rectrices firm, with very rigid and 
more or less extruded shafts; tarsus longer than middle toe with 
claw; middle and outer toes equal in length, the inner toe very 
slightly shorter; hallux (without claw) more than half as long as 
inner toe (without claw).? 
Coloration.—Plain blackish or sooty, the adults with a white 
collar, at least across hindneck. 
@ From otpentéc, torquis, and zpdmn, Progne. (Oberholser.) 
b A peculiarity in the myology of Streptoprocne is thus described by Dr. F. A. Lucas 
in The Auk, xvi, 1899, 97: 
It might be supposed that the anatomical possibilities of so small a group as the 
Swifts had been exhausted, but that this is not the case is shown by an examination 
of Hemiprocne zonaris, for which I am indebted to Mr. C.B. Taylor, of Jamaica. The 
cranium is typically cypseline, so are the wing muscles, although the deltoid is small, 
as in the majority of the true Swifts, there being an apparent tendency to reduction 
in the number of wing muscles in birds which fly, so to speak, by main strength and 
in which the humerus is reduced in length. The leg muscles are curious first by the 
absence of the peroneus longus, « muscle which runs from the head of the tibia to 
the upper end of the tarsus in Passeres, and second by the great simplification of the 
deep plantar tendons. In the Passeres, as we all know, one tendon flexes the first 
digit of the foot, while another with three branches flexes the three front toes. In 
the Tree Swifts, Macropterygide, the tendon of the hind toe is attached by a short 
slip to the branch running to the fourth digit. In the other Swifts so far examined 
the two main tendons are completely fused for some distance although worked by two 
muscles. Now in Hemiprocne [i. e., Streptoprocne] while the muscle which ordinarily 
works the front toes, the flexor perforans, is present, it has no separate tendon, but is 
attached to the muscle of the first digit, flexor longus hallucis, and is diverted to the 
work of pulling on its tendon, which as usual runs up over the outer side of the belly 
of the muscle. Below this single tendon sends off four slips, one to each digit, thus 
presenting the simplest condition possible and literally realizing Gadow’s statement 
that the flexor longus hallucis is really a common flexor of all digits. Ifa good generic 
character is needed for Hemiproene [Streptoprocne], here it is. 
