In lateral aspect, the carina is deeper in _Bombycilla_ than in other genera of the family, and is deepest in _B. garrula_. In this species, the manubrium is more extended and comparatively larger than in the other species of the family. The anterior edge of the keel forms the sharpest angle in _B. cedrorum_. In _Dulus_, the keel is moderately deep, the manubrium short, and there is a distinct indented curve between the manubrium and the anterior angle of the keel. In ventral aspect the lateral processes of the sternum tend to flare outwards in adult Ptilogonatines on almost the same plane as the rest of the bone, whereas in _Bombycilla_ and _Dulus_ the same process is closer to the body of the sternum. In _Bombycilla_ the xiphoid process is more dorsal in position than in other species in the family, and in _Dulus_ an upward curve is very noticeable. The process in these two genera is narrower than in the Ptilogonatinae, and lacks the heavy distal terminal enlargement which is apparent in _Ptilogonys_. _Relative Lengths of Bones._--In instances where the animals being compared are obviously different in over-all size, it is useful to express the size of a given part in relation to some other part of the same individual organism if the aim is to obtain clues as to differences in functions of the parts being compared. Differences in actual lengths of corresponding bones in two kinds of animals often, of course, reflect only the difference in over-all size of the animals. Consequently, the relative size of the part is expressed as a percentage in this paper. In computing a percentage it is well, of course, to select some relatively stable part of the animal to use as a denominator in the mathematical expression that yields the percentage. The thoracic region of the vertebral column is thought to be such a part. For example, the length of the humerus divided by the length of the thoracic region yields, in _Phainopepla_ and _Ptilogonys_, respective percentages of .84 and .85. These are roughly the same, whereas the actual lengths of the humeri are 2.21 and 2.39 cm. Table 4. Lengths of Leg Bones in cm. =========================+=======+=============+================= Species | Femur | Tibiotarsus | Tarsometatarsus -------------------------+-------+-------------+----------------- Ptilogonys caudatus | 2.04 | 3.10 | 1.94 Ptilogonys cinereus | 1.89 | 2.90 | 1.77 Phainopepla nitens | 1.76 | 2.78 | 1.72 Phainoptila melanoxantha | 2.43 | 3.77 | 2.58 Dulus dominicus | 2.09 | 3.34 | 2.09 Bombycilla garrula | 2.32 | 3.46 | 1.99 Bombycilla cedrorum | 1.92 | 2.95 | 1.64 -------------------------+-------+-------------+----------------- Table 5. Leg-trunk Ratios (in percent)