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Show 1890.] HELODERMA SUSPECTUM. 189 I have failed to find a peroneus primus present in Heloderma. Sanders found one present in Phrynosoma, and Mivart one in Lguana, and I believe it is usually present in Lizards. 104. Extensor longus digitorum.-Occupying a conspicuous and median position upon the anterior aspect of the leg, this muscle arises by a strong, flat tendon which comes off from the external condyle of the femur, passes down in front of the same, and below the femoro-tibial articulation becomes a comparatively flat and narrow muscle, continuing thus to the tarsus. In this latter locality its tendon begins to form, and, when over the metatarsus, this latter splits into two other delicate tendons. Mivart found the same bifurcation in Lguana tuberculata, and he has said that, " Of these two tendons, the peroneal one curves round tibiad, and is inserted into nearly the middle of the plantar surface of the third metatarsal ; " the other one is similarly implanted into the second metatarsal. This agrees precisely with what we find in Heloderma. 105. The tibialis anticus is a muscle of the interno-lateral aspect of the leg in this reptile. Arising from the antero-lateral surface of the shaft of the tibia, from the side of the head of the bone, and to some extent from the fascia at the tibial side of the knee-joint, the tibialis anticus forms a fleshy muscle at the inner rather than at the anterior aspect of the leg. At about the middle of its course it is quite intimately connected with the internal head of the gastrocnemius, at the origin of the latter from the tibial shaft. Opposite the ankle the present muscle again becomes tendinous, and this, its tendon of insertion, passes to the distal extremity of the first metatarsal bone, where, upon the tibial side of its dorsal aspect, it is inserted. It appears to be quite generally the case among Lizards that the tibialis anticus occupies an antero-lateral position upon the leg, rather than a mid-anterior one as it does in so many of the Mammalia. 106. Extensor brevis digitorum.-We find this muscle to some extent quite complicated, and it arises by several independent slips, which have diverse origins and insertions. Their disposition seems to be as follows : - (1) An oblique fasciculus that arises from the anterior surface of the distal end of the fibula, and which, passing forwards and inwards across the top of the foot, is inserted into the superior surface of the proximal phalanx of the hallux. (2) A smaller fasciculus than the last, also arises from the fibula below it but more particularly from the fibulare (of the co-ossified bones of the proximal row), and, passing directly forwards, becomes inserted upon the dorsal aspect of the proximal joint of the fifth digit. (3) Fasciculus number three arises from the antero-superior surface of the mid-ossicle of the distal tarsalia, it passes between the bifurcated tendon of the extensor longus digitorum, and arriving at the third digit it makes an insertion upon the upper surface of its proximal phalanx. PROC. ZOOL. Soc-1890, No. XIV. 14 |
