[Illustration: FIG. 1. _Pipilo erythrophthalmus._ Lateral view of the superficial muscles of the left leg, × 1.5.]
[Illustration: FIG. 2. _Pipilo erythrophthalmus._ Lateral view of the left leg showing a deeper set of muscles. The superficial muscles _iliotibialis_, _sartorius_, _gastrocnemius_ and _peroneus longus_ have been removed, × 1.5.]
[Illustration: FIG. 3. _Pipilo erythrophthalmus._ Lateral view of the left leg showing the still deeper muscles. In addition to those listed for figure 2, the following muscles have been wholly or partly removed: _iliotrochantericus posticus_, _femorotibialis externus_, _femorotibialis medius_, _biceps femoris_, _semitendinosus_, _tibialis anticus_, _flexor perforans et perforatus digiti II_, and _flexor perforans et perforatus digiti III_, × 1.5.]
[Illustration: FIG. 4. _Pipilo erythrophthalmus._ Medial view of the superficial muscles of the left leg, × 1.5.]
[Illustration: FIG. 5. _Pipilo erythrophthalmus._ Medial view of the left leg showing a deeper set of muscles than those seen in figure 4. The following superficial muscles have been removed: _iliotibialis_, _sartorius_, _femorotibialis internus_, _obturator internus_, _adductor longus (pars posticus)_, _gastrocnemius_, and _peroneus longus_, × 1.5.]
[Illustration: FIG. 6. _Pipilo erythrophthalmus._ Proximal end of left tarsometatarsus and the hypotarsus, × 4.]
[Illustration: FIG. 7. _Pipilo erythrophthalmus._ Lateral view of proximal end of left femur and a portion of the pelvis, × 3.5.]
[Illustration: FIG. 8. _Pipilo erythrophthalmus._ Upper surfaces of the phalanges of the foretoes of the left foot showing insertions of the _M. extensor digitorum longus_, × 3.]
[Illustration: FIG. 9. _Pipilo erythrophthalmus._ Medial view of the second digit of the left foot, showing insertions of the flexor muscles, × 3.]
The division of the _pars interna_ of the _m. gastrocnemius_ into anterior and posterior parts has not been reported by previous authors yet the division is quite distinct in those birds in which it occurs. Hudson (1937:36) points out that in some non-passerine birds the _pars interna_ is double, but that in these species the _m. semimembranosus_ inserts between the two parts. This is not the condition in those species studied by me. Only the ploceids and the cardueline finches in the present investigation fail to show such a division. The undivided muscle in these birds resembles, in its origin and position, the posterior portion of the muscle found in those species showing the bipartite condition. The greater mass of the bipartite muscle probably makes possible a stronger extension of the tarsometatarsus.