1890.] HELODKRMA SUSPECTUM. 189 



I have failed to find a peroneus primus present in Hdoderma. 

 Sanders found one present in Phrynosoma, and Mivart one in Iguana, 

 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 Iguana 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 gastro- 

 cnemius, 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 Mam- 

 malia. 



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) Fascicuhis 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. 



Pkoc. Zool. Soc— 1890, No. XIV. 14 



