_+Musculus obturator internus+_ (Figs. 4, 7).--Lying on the inside of the pelvis and covering the medial surface of the ischiopubic fenestra, is this flat, pinnate, leaf-shaped muscle. The origin is fleshy and is from the ischium and pubis around the edges of this fenestra; none of the fibers arises from the membrane stretched across the fenestra. Anteriorly the fibers converge and form a strong tendon that passes through the obturator foramen and inserts on the posterolateral surface of the trochanter of the femur. Action.--Rotates femur posteriorly. Comparison.--No significant differences noted among the species studied. _+Musculus obturator externus+_ (Fig. 7).--Short and fleshy, this muscle consists of two parts which are not easily separable but which may be traced throughout its length. The parts are more nearly distinct at the origin. The dorsal part arises directly from the ischium along the dorsal edge of the obturator foramen. The larger ventral part arises directly from the anterior and ventral edges of the obturator foramen. The fibers of the dorsal part pass anteriorly, cover the tendon of the _m. obturator internus_ laterally, and insert on the trochanter around the point of insertion of the latter muscle. The fibers of the ventral part pass parallel with the tendon of the _m. obturator internus_ and insert on the trochanter immediately distal and posterior to the tendon of the latter muscle. Action.--Rotates femur posteriorly. Comparison.--In _Passer_, _Estrilda_, _Poephila_, _Hesperiphona_, _Carpodacus_, _Pinicola_, _Leucosticte_, _Spinus_ and _Loxia_, this muscle is undivided and, in its position, origin, and insertion, resembles the ventral part of the bipartite muscle described above. The origin is from the anterior and ventral edges of the obturator foramen and the insertion is on the trochanter of the femur immediately distal and posterior to the insertion of the _m. obturator internus_. In all other genera examined, the muscle is bipartite. In _Chlorura_ the dorsal part is larger and better developed than it is in the other genera. _+Musculus adductor longus et brevis+_ (Figs. 3, 4, 5).--Consisting of two distinct, straplike parts, this large muscle lies on the medial surface of the thigh, posterior to the femur. The _pars anticus_ has a semitendinous origin on a line that extends posteriorly from the posteroventral edge of the obturator foramen to a point half way across the membrane that covers the ischiopubic fenestra. The insertion is fleshy along the posterior surface of the femur from the level of the insertion of the _m. piriformis_ distally to the medial surface of the internal condyle.