910 DR. R. W. SHUFELDT ON THE OSTEOLOGY OF THE [DcC. 1, 



their composition goes, are more generally known, and the characters 

 they present have been enlisted by ornithologists from time imme- 

 morial to serve the purposes of classification. 



Thanks to this being the case, references to the member in the 

 present instance can be made much briefer than in the case with the 

 pectoral limb, and still fully meet our purpose. 



In Whippoorwills and Night-hawks the bones of this extremity 

 are always non-pneumatic, and, with the exception of rather a short 

 tarso-metatarsus, harmoniously proportioned as to lengths and calibre. 



ChordeJiles possesses nearly a straight shaft to its femur, which 

 is smooth, and quite cylindrical. The trochanterian ridge does not 

 rise above the articular summit of the bone, and of the condyles at 

 its distal extremity the external one is the lower. 



A patella seems to be wanting in these birds, its place being filled 

 by a bit of cartilage in the tendon. 



The shaft of tibio-tarsus is likewise straight and subcylindrical ; 

 the chief point of interest iu this bone, however, is the complete 

 suppression of the ectocnemial ridge, while the procnemial one seems 

 to have moved to a more central position on the shaft. 



A not very strong fibula fails to anchylose with this latter below, 

 and makes unusually weak connections with it above. 



Tarso-metatarsus has a subcubical hypotarsus, apparently un- 

 pierced by the flexor tendons , otherwise this segment presents 

 nothing worthy of special record. A. well-developed accessory meta- 

 tarsal is attached in the usual way, rather high on the shaft, by liga- 

 ment. The formula for the podal digits, being 2, 3, 4, 4, is well 

 known and requires no particular mention. 



In the delicate pelvic limb of Trochilus we also find a non-pneu- 

 matic /emMr with straight and cylindrical shaft, and with the charac- 

 ters of the extremities much as in the Goatsuckers. Humming-birds, 

 however, have a large, free patella developed, of the most usual form. 



In them the fibula remains independent of the main leg-bone, but 

 is notably short and puny. 



Tibio-tarsus has nearly a straight shaft, and carries the peculiarity 

 seen in C/iordediles one point further, in having both the cnemial 

 ridges so feebly pronounced as hardly to be noticed, unless specially 

 searched for, when only faintest traces of the procnemial ridge 

 become evident. The usual osseous bridge confines the exteusor 

 tendons at the distal end of this bone. 



The hypotarsus of the tarso-metatarsus is both pierced and 

 grooved for the transmission of the flexor tendons, and the free 

 accessory metatarsal is suspended high upon its shaft. 



In number and arrangement the joints of the digits of pes agree 

 with the formula of the typical Passerine foot, and are here most 

 noted for the unusual lengths of the ungual phalanges when com- 

 pared with the basal and remaining joints. 



While the pelvic limb in the Swallows seems to be constructed 

 after tlie true Passerine type, in the Swifts it makes a marked de- 

 parture from this, presenting at the same time a number of points of 

 no little interest. 



