140 U. S. p. R. R, EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



Family CYPSELIDAE. The Swifts. 



Bill very small, without notch, triangular, much broader than high ; the culmen not one-siith the gape. Anterior toes cleft 

 to the base, each with three joints, (in tlie typical species,) and covered with skin ; the middle claw without any serrations ; the 

 lateral toes nearly equal to the middle. Bill witliout bristles, but with minute feathers extending along the under margin of the 

 nostrils. Nostrils elongated, superior, and very close together. Plumage compact. Primaries ten elongated, falcate. 



The Cypselidae, or Swifts, are swallow-like birds, generally of rather dull plum ge and small 

 size. They were formerly associated with the true swallows en account of their small, deeply 

 cleft hill, short feet, and long wings. Ti ey are, however, very different in all the essentials of 

 structure, belonging indeed to a different order, or sub-order. The bill is much smaller and 

 shorter ; the edges greatly inflected ; the nostrils superior, instead of lateral, and without 

 bristles. The wing is more falcate, with ten primaries instead of nine. The tail has ten 

 feathers instead of twelve. The feet are weaker, without distinct scutellae ; the hind toe is 

 more or less versatile, the anterior toes usually lack the normal number of joints, and there are 

 other features which clearly justify the wide separation here given, especially the difference in 

 the vocal organs. 



There are some forms of Cypselidae in which the usual proportional length of toes and number of 

 their joints is as in other birds ; nearly all the typical Old World genera, however, agree with the 

 diagnosis above given. It is exceedingly probable, however, that the American genera have all 

 the normal number of joints to the anterior toes, (3, 4, 5,) Panyptila, probably, not even form- 

 ing an exception ; in this case they will be widely separated from the great majority at least, of 

 the Old World species, which have 3, 3, 3. It may therefore be proper, on account of these 

 and other differences, to divide the family into Cypselinae, confined to the Old World, and 

 Chaeturinae, American and Asiatic. 



The American Cypselidae are readily distinguished by characters of the legs, and including 

 the Old World Cypselus, which has no true representative in this country, convenient diagnoses 

 of the genera will be as follows, without reference to other features : 



A. Legs very thick, more or less feathered. Tail forked. Second primary longest. Ilind 

 toe not posterior. 



Cypselus. — Hind toe directed entirely forward. Legs feathered to the base of the toes. 

 Pantptila. — Hind toe directed laterally. Legs feathered to the base of the claws. 



B. Legs slender : naked. Hind toe directed backwards ; first primary longest. 



Nephocaeies. — Tail forked ; soft. 



Chaetura. — Tail even, the" shafts stiffened and projecting as spinous points. 



PANYPTILA, Cabanis. 



Panyptila, Cabanis, Wiegm. Arcliiv, 1847, i, 345. — Burmehter, Thiore Uras. Viigel, I, )85G, 368. 

 Paeudoprocne, Strehbll, lais, 1848, 357. 



Tail half as long as the wings, moderately forked ; the feathers rather lanceolate, rounded at lip, the shafts stifTened but not 

 projecting. First primary shorter than the second. Tarsi, toes, and claws very thick and stout ; the former shorter than the 

 middle too and claw, which Is rather longer than the lateral one ; middle claw longer than its digit. Mind toe very short ; half 

 versatile, or inserted on the side of the tarsus. Tarsi and toes feathered to the claws, except on the under surfaces. 



The North American representative of this genus, with a general rescinbhuice to Cijpsdiis 

 apus in form, is quite dilferent in tlie structure of the feet These are stouter and shorter, 

 feathered to the very claws, instead of to the toes only, and the posterior or inferior surface of 



