MUSCULATURE. 279 



The adductor femoris (Plate 2, fig. 4, af) has the usual two heads, magnus 

 and brevis. The former arises along the caudal margin of the ischium, in part 

 covered by the semimemhranosus, from the tuberosity for slightly more than 

 half the distance to the posterior end of the sjTiiphysis pubis. It inserts partly 

 along the medial and posterior side of the distal end of the shaft of the femur, 

 and in part bj^ tendon in common with the hrevis division on the medial epi- 

 condyle of the femur luider co^■er of the sartorius. The brevis division arises 

 along the symphysis pubis under cover of the gracilis. Its insertion is m part 

 by the conmion tendon and thence proximalh* on the middle thu'd of the femur. 



The adductor longus (Plate 2, fig. 4, al) is wanting in the Echidna, but in 

 the Proechidna seems to be repre.sented by a short compressed muscle arising 

 from the external base of the epipubis. It is inserted along the medial edge of 

 the distal third of the femur in close association with the pectineus. 



The -pectineus (Plate 2, fig. 4, pec) is a somewhat similar muscle arising 

 just dorsal to the adductor longus, on the anterior edge of the pubis. Its inser- 

 tion is m close approximation with that of the latter, on the medial edge of 

 the femur, but is slightly shorter. • 



The rectus femoris (Plate 2, fig. 4, /•/) is from the ilium just anterior to the 

 acetabulum and passes to its insertion into the proximal border of the patella 

 and the fascia ensheathing the knee. 



The vastus lateralis arises by muscular fibers from the whole anterolateral 

 side of the femur from the median Ime to the trochanteric ridge. It inserts 

 upon the lateral edge of the patella and becomes fused distally with the rectus 

 femoris and vastus medialis. 



The vastus inedialis (Plate 2, fig. 4, va) is slightly smaller than the lateralis, 

 and takes origin from the anteromedial portion of the shaft of the femur. It 

 is partly fused with the two precedmg muscles distallj^ and inserts also on the 

 medial side of the patella. A vastus 'intermedius is not to be distinguished in 

 either the Proechidna or the Echidna. 



The muscles of the lower leg are weak and slender. The gastrocnemius 

 (Plate 2, fig. 4, gas) has much the same relations as in the Echidna. There is 

 but a single head, from the ventral side of the medial tubercle of the femur, 

 a flat narrow muscle that passes into a flat tendon on the lower half of the leg, 

 and is inserted into the calcaneum at its external border. 



The soleus (Plate 2, fig. 4, so) is a similarly shaped muscle, arising from the 

 external side of the ascending proxunal end of the fibula. Its tendon becomes 

 bound by connective tissue to that of the gastrocnemius, and the two pass side 



