INDIVIDUAL VARIATION.--In both legs of one specimen, the part arising from the femorofibular fascia appears as a distinct but short accessory head. There is no significant individual variation in _T. cupido_ or _P. p. jamesi_. =_M. Flexor Perforatus Digiti IV_=, Figs. 14, 16 _T. pallidicinctus_ GENERAL DESCRIPTION AND RELATIONS.--On posterolateral aspect of shank deep to M. gastrocnemius pars externa; bounded medially by medial head of M. flexor perforatus digiti III, anterolaterally by posterior head of M. flexor perforans et perforatus digiti II, and anteriorly by M. flexor digitorum longus; divided into three heads--medial (largest), lateral, and anterolateral (smallest); tendon of insertion of M. extensor iliofibularis passing between medial and lateral heads; proximal and anteroproximal parts of _lateral head_ an extremely thin, flat tendon; anterodistal part of tendon fused to lateral surface of fleshy part of underlying lateral head of M. flexor perforatus digiti II; proximal part of tendon fused indistinguishably to tendinous part of underlying lateral head of M. flexor perforatus digiti II; fleshy part of _anterolateral head_ anterodistal to lateral head; proximal part of former a long slender tendon anterior to lateral head; anterior surface of anterolateral head (both fleshy and tendinous parts) fused to tendon of anterolateral head of M. flexor perforatus digiti III; deep surface fused to underlying anterolateral head (fleshy) of M. flexor perforatus digiti II; common tendon of anterolateral heads of M. flexor perforatus digiti IV and M. flexor perforatus digiti III passing medial to tendon of insertion of M. extensor iliofibularis, to peroneal nerve, and to fibular arm of guide loop for M. extensor iliofibularis; tendon of M. ambiens inserting on anterolateral surface of this common tendon; _medial head_ entirely fleshy; medial surface fused to medial head of M. flexor perforatus digiti III; deep surface fused to medial edge of underlying medial head of M. flexor perforatus digiti II; medial and lateral heads joined, forming bipinnate belly (pinnate structure most evident on deep surface); anterolateral head joined to distolateral part of belly. ORIGIN.--The _medial head_ attaches fleshily to the proximal part of the popliteal area proximal (adjacent) to the origin of M. flexor hallucis longus and distolateral to the distal end of the origin of M. femorocruralis; the attachment extends laterally onto the posterolateral surface of the femur proximal (adjacent) to the common attachment of M. gastrocnemius pars externa and the distal arm of the guide loop for M. extensor iliofibularis; the medial edge of the origin is fused with part of the tendinous origin of the medial head of M. flexor perforatus digiti III.