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Show 908 DR. R. W. SHUFELDT ON THE OSTF.OLOGY OF THE [DeC. 1, presenting all the characters of this part common to the avian brachiurn. As will be seen from the figure, the ulna and radius present nothing peculiar. The free bones in the carpus are two in number, as is the rule for birds. The metacarpus offers us nothing worthy of special note, as may be seen from the drawing. The pollex-phalanx is composed of but one joint, the index-digit of two ; and the usual small one in the next finger. The expanded portion of the proximal phalanx of the index shows two perforations ; these run into one large one in Nuttail's Whippoorwill-a rare condition. This last-named bird has the skeleton of its arm, with the exception of this one detail, agreeing in all essential respects with the bones just described. Pneumaticity does not extend beyond the humerus in true Caprimulgida. Turning our attention to the Plumming-birds, we find that the humerus in Trochilus is a most extraordinary structure, departing, as it does, both in form and proportions, from that bone as it occurs in most birds. The humeral head for the glenoid cavity has much the same contour as elsewhere in the class ; but the radial crest is represented by a strong and gracefully curved hook curling over in the direction of the shaft. Another prominent process points forwards and outwards, which has its base just beyond the distal portion of the periphery of the pneumatic foramen. Eccentricities of form are none the less evident in the shaft of this unique bone. This is of a quadrilateral outline, broadly oblong, and somewhat curiously twisted. The trochleae of the distal end are very prominent, while opposite them on the anconal aspect, is found, holding a mid position, a deep and rounded excavation. In life this harbours a large sesamoid ; and another, about one third its size, is at the elbow (Plate LXI. figs. 3 s, s'). The radius and ulna are but little longer than the humerus ; the former is much bowed, giving rise to a large "interosseous space" when these bones are duly articulated. The ulna is nearly straight, having a stout, subcylindrical shaft; and notwithstanding the presence of the sesamoid in the olecranon fossa of the humerus, the process of this name is well developed upon it. Two small sesamoids are found about the carpal joint (s", s'"), while its true elements, the ulnare and radiate, are manifestly different from these segments in ordinary birds, the former in being almost devoid of the characteristic apophyses, and the latter in being less angular. This Humming-bird has a metacarpus notably longer than the bones of its antibrachium. Its index and midshaft are quite straight (i1, ni), the latter being produced further distallv. and supporting a considerable facet for its unusually long finger-joint m" (compare with figure 4). The pollex-digit has but one joint (/>), two being awarded to the index, the proximal one of the latter having its blade portion very much expanded and a mid process (j) at its lower margin-an uncommon site for it. Comparing these points in the skeleton of the arm of T. alexandri, |
