 Figure 6 | |
 Figure 8 |  Figure 7 |
 Figure 9 |
Fig. 6. Pipilo erythrophthalmus. Proximal end of left tarsometatarsus and the hypotarsus, × 4.
Fig. 7. Pipilo erythrophthalmus. Lateral view of proximal end of left femur and a portion of the pelvis, × 3.5.
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.
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.