MUSCULATURE. 279 
The adductor ae (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 semimembranosus, from the tuberosity for shghtly more than 
half the distance to the posterior end of the symphysis pubis. It inserts partly 
along the medial and posterior side of the distal end of the shaft of the femur, 
and in part by tendon in common with the brevis division on the medial epi- 
condyle of the femur under cover of the sartoriws. The brevis division arises 
along the symphysis pubis under cover of the gracilis. Its insertion is in part 
by the common tendon and thence proximally on the middle third of the femur. 
The adductor longus (Plate 2, fig. 4, al) is wanting in the Echidna, but in 
the Proechidna seems to be represented 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 in 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, rf) 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 line 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 medialis (Plate 2, fig. 4, va) is shghtly smaller than the lateralis, 
and takes origin from the anteromedial portion of the shaft of the femur. It 
is partly fused with the two preceding muscles distally 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 caleaneum at its external border. 
The soleus (Plate 2, fig. 4, so) is a similarly shaped muscle, arising from the 
external side of the ascending proximal end of the fibula. Its tendon becomes 
bound by connective tissue to that of the gastrocnemius, and the two pass side 
