_+Musculus flexor hallucis longus+_ (Fig. 3).--Situated immediately posterior to the _m. flexor digitorum longus_, the belly of this large, pinnate muscle is intimately connected anteriorly to that of the _m. flexor perforatus digiti II_. The _m. flexor hallucis longus_ arises by two heads which are separated by the tendon of insertion of the _m. biceps femoris_. The smaller anterior head arises from the same tendon as does the _m. flexor perforatus digiti II_. The larger posterior head arises by means of fleshy fibers from the intercondyloid region of the posterior surface of the femur along with the _m. flexor perforatus digiti III_ and _IV_. The two heads join just distal to the point of insertion of the _m. biceps femoris_. There is no trace of a tendinous band connecting the two heads as there is in the crow and in the raven (Hudson, 1937:49). Near the distal end of the shank the muscle gives rise to a strong tendon which perforates the tibial cartilage along its lateral edge and passes through the anterolateral canal of the hypotarsus (Fig. 6). The tendon crosses over to the medial surface of the tarsometatarsus, passes distally, and perforates the sheathlike tendon of the _m. flexor hallucis brevis_ between the first metatarsal and the trochlea for digit II. The tendon continues along the posterior surface of the hallux and has a double insertion; the main tendon attaches to the base of the ungual phalanx and a smaller branch inserts on the distal end of the proximal phalanx.
Comparison.--In _Vireo_ this muscle has only the posterior head of origin and is not connected with the _m. flexor perforatus digiti II_. The muscle is proportionately smaller and weaker than in any of the other species studied.
_+Musculus extensor hallucis longus+_ (Fig. 4).--One of the smallest muscles of the leg, the origin is fleshy from the anteromedial edge of the proximal end of the tarsometatarsus. The belly is long and slender and terminates distally in a slender tendon which passes distally along the posterior surfaces of the first metatarsal and the first digit. The insertion is on the base of the ungual phalanx. Near the distal end of the proximal phalanx, the tendon passes between two thick bands of fibro-elastic tissue which insert also on the ungual phalanx. These bands of tissue function as automatic extensors of the claw.