OCR Text |
Show 1885.] TROCHILID.E, CAPRIMULGIDiE, AND CYPSELID^E. 909 with the similar points in the corresponding limb of Panyptila saxa-tilis as shown in figure 4, we find that scarcely one of them exactly agrees with the other. Indeed, the differences are very striking and important, and far greater than commonly occur among birds generally. To commence with, the humerus in the Swift, though short, is of entirely a different form. Its radial crest curves towards the humeral head ; the ulnar crest is powerfully developed, though the fossa it arches over contains no pneumatic opening, the bone not enjoying this property as does the humerus in Trochilus. Again, the apophysis at the base of this fossa is not found in the Swift as it was in the Humming-bird, though in the former a distinctive tubercle occurs beyond the base of the radial crest, which is absent in the latter. The olecranon fossa is even deeper and better defined than in Trochilus, though I have failed to find any of the sesamoids present in the limit of that little bird ; and among these the large one which corresponds to the one marked * in figure 3. Panyptila has the oblique and ulnar tubercles of this distal humeral extremity also markedly protuberant. Radius and ulna are here both very straight, and differ from the Humming-bird in being appreciably longer than the bone of the brachium. TJlnare and radiate segments of the carpus deviate but slightly from the general contour of these bonelets in Passeres, and still less from them as found in some Swallows. Metacarpus is comparatively large and heavy, its form being well shown in fig. 4. It will likewise be observed that the digital formula agrees with the Trochilida, as it does with Passerine types ; the individual bones, however, have forms peculiar to themselves. These can be best appreciated by a study of them in the Plate, and far better than can be conveyed in any written description. Pluxley, in alluding to the relative lengths of the bones of the pectoral limb in the Trochilida and Cypselida, says that the " two families have a length of the manus and a brevity of the humerus which is peculiar to themselves, being only approached by the Swallows, and in a less degree by the Caprimulgida. " In both Caprimulgus and Mgotheles the manus is slightly longer than the ulna, and the latter considerably exceeds the humerus in length." * M y studies of the skeletons of American forms of these several families fully bear out the results of the investigations of this eminent biologist upon this point. Owing to the fact that the structure of the foot and certain parts of the pelvic limb can be studied from external inspection with results far more satisfactory than can be hoped for, from the very nature of things, from an equal amount of attention paid to the wing of a bird, it stands to reason that, as a rule, these parts, so far as i " On the Classification of Birds," P. Z. S. 1867, p. 469. P R O C ZOOL. Soc-1885, No. LIX. 59 |