278 ZAGLOSSUS. 
The iliopsoas is a large mass from two heads:—(1) the iliac portion which 
arises from the ventral side of the ilium from its tuberosity nearly half way to 
the acetabular notch; (2) the psoas portion from the three last lumbar verte- 
brae. The common insertion is by muscular and tendinous fibers into the 
lesser trochanter for about one half the distance between the lesser trochanteric 
head and the distal epiphysis of the femur. In the Echidna the psoas portion 
has origin from the three last lumbars and first sacral, but in the Proechidna 
the origin seems to be from the lumbars only. 
The psoas minor arises from three heads, one each from the two last dorsal 
and the first lumbar vertebrae. The most anterior of these heads extends 
laterally on to the proximal end of the rib. The muscle narrows to a powerful 
tendon that inserts as usual on the anterior edge of the pubis directly in front 
of the acetabulum. In the Echidna the origin is slightly different, according to 
Mivart, ‘‘from the last three ribs, and....the bodies of the last three dorsal 
vertebrae.”” This difference may be correlated with the presence of an addi- 
tional lumbar in the Proechidna. 
The biceps femoris (Plate 1, fig. 1, bf) as in the Echidna, arises from a single 
head, by stout tendon from the lateral portion of the ischial tuberosity. It 
forms a flat sheet of muscle, triangular in outline and is broadly inserted along 
the lateral margin of the proximal three fourths of the tibia into the sheet of 
fascia investing the lower leg, and by a thin tendinous sheet continuous with 
this, into the lateral margin of the patella. 
The semitendinosus (Plate 2, fig. 4, st) is from the lateral edge of the ischial 
tuberosity, a broad flattened band, inserting by muscular and tendinous fibers 
on the medial border of the tibia underneath the insertion of the gracilis. 
The semimembranosus (Plate 2, fig. 4, sm) is a somewhat similar broad 
muscle, arising by tendinous fibers directly underneath the origin of the sem- 
tendinosus, on the tuberosity of the ischium. It inserts by a stout tendon on 
the medial surface of the head of the tibia. 
The sartorius (Plate 2, fig. 4, sa) takes origin as a flat thin band for about 
10 mm. along the anterior edge of the pubis just dorsal to the epipubic bone. 
It passes to the fascia investing the knee at the medial border of the distal 
head of the femur and the proximal head of the tibia. 
The gracilis (Plate 2, fig. 4, 7) muscles of opposite sides are separate medially. 
Each arises as a broad flat muscle from the basal one sixth of the epipubic bone, 
the entire pubic symphysis, and for a short distance on the ramus of the ischium. 
It inserts on the medial face of the tibia at the beginning of its second fourth. 
