_+Musculus flexor perforatus digiti II+_ (Figs. 3, 9).--This is a slender muscle which lies on the lateral side of the crus beneath the _pars externa_ of the _m. gastrocnemius_ and is intimately connected anteromedially with the _m. flexor digitorum longus_ and posteromedially with the _m. flexor hallucis longus_. The origin is by a strong tendon from the lateral surface of the external condyle of the femur at the point of origin of the _m. flexor perforans et perforatus digiti II_. This tendon serves also as the origin of the anterior head of the _m. flexor hallucis longus_. The tendon connects also by a broad tendinous band with the distal arm of the loop for the _m. biceps femoris_ and by a similar band with the lateral edge of the fibula immediately distal to the head. The tendon of insertion passes distally, perforates the tibial cartilage near its lateral edge, traverses the middle medial canal of the hypotarsus (Fig. 6), and passes distally to the foot. At the distal end of the tarsometatarsus the tendon is held against the medial surface of the first metatarsal by a straplike sheath. The tendon then passes over a sesamoid bone between the first metatarsal and the base of the second digit and is bound to this bone by a sheath. The tendon inserts mainly along the posteromedial edge of the proximal end of the first phalanx of the second digit, although the termination is sheathlike and covers the entire posterior surface of this phalanx. This sheathlike termination is perforated by the tendons of the _m. flexor perforans et perforatus digiti II_ and the branch of the _m. flexor digitorum longus_ that inserts on the second digit. Action.--Flexes second digit. Comparison.--In _Vireo_ this muscle is larger and more deeply situated than it is in the other species examined and has no connection with the _m. flexor hallucis longus_.