NEW PERMIAN VERTEBRATES 653 
bles an italic letter L, with the intercondylar groove in front deep, 
the popliteal groove shallow. In front, the outer border is convex to 
the articular surface for the fibula, and the articular surface as a 
whole is directed ventrad at an angle of about forty-five degrees from 
the long axis of the femur, and also outward at an angle of about 
twenty degrees; the articular surface also extends proximad on the 
ventral side so as to permit a considerable degree of flexion, while com- 
plete extension would have been impossible. The considerable 
depth of the pelvic symphysis raised the acetabular surface some 
distance from the ground, and doubtless the knee was constantly 
flexed to a considerable extent. 
The tibia is preserved in the matrix in articulation with both the 
femur and tarsus, but rotated somewhat upon its outer side. Its 
proximal extremity is much expanded, antero-posteriorly, and also 
somewhat from side to side. Its articular surface for the femur is 
slightly concave, sloping obliquely backward and outward from the 
long axis. Its proximal part in front is broad for the insertion of the 
stout muscles of the intercondylar groove, while a large surface pos- 
teriorly also gave insertion to the flexor muscles. The middle of the 
shaft of the bone is slender, and nearly circular in cross-section, from 
which place the bone becomes gradually broader to the distal end, 
which is thickened and broader from side to side than from before 
back. The outer border of the bone, as a whole, is nearly straight, 
or gently concave; the inner border is deeply concave. 
As already stated, the fibula was dislodged from its position. 
Lying close by the inner side of the tibia, is a flattened bone, imperfect 
at one side, which is evidently the distal extremity of a fibula. The 
part preserved is remarkably broad, much thinner on its outer side, 
thickened, shaft-like on the inner, where broken off. Distally it 
shows two thickened, apparently articular borders separated by a 
thinner, non-articular margin. x 
The tarsus and foot lie almost perfectly in position, the tibiale 
slightly turned outward by the rotation of the tibia, and the fifth toe 
partially turned under the fourth and third. Lying as they do upon 
the sides of the fourteenth, fifteenth, and sixteenth vertebrae, the bones 
are somewhat uneven, because of the rugosities. There are twelve 
tarsal bones, three in the proximal, four in the middle, and five in the 
