From Cottonwood Creek.
Orohippus major? Marsh.
Femur ([Plate IX.], Fig. 1).—The femur has a small, nearly hemispherical head, developed on a long and slender neck; the head is but slightly out of the axis of the shaft, and has a large pit for ligamentous insertion. The shaft is long, simple, and curved slightly forward. At the proximal end it is broad and flattened axially; below this it becomes expanded fore-and-aft, but it thickens greatly at the distal end, just above the condyles. The great trochanter is large and retroverted, rising above the head, with two prominences rising from it, one on top, the other back. The digital fossa is wide and deep, penetrating far into the great trochanter. The second trochanter is a small rounded ridge; the third trochanter is large and prominent, curving slightly forward. The condyles are long and narrow, projecting very far back, and are separated by a wide and deep popliteal groove. From the external condyle a low ridge runs obliquely, forming the upper border of the shallow popliteal space. The trochleæ are long, very convex, deeply grooved, and symmetrical.
Measurements of Femur.
| M. | |
| Width between head and great trochanter | ·019 |
| Width at third trochanter | ·034 |
| Diameter of head | ·019 |
| Width at condyles | ·028 |
| Width of trochlea | ·015 |
| Height of great trochanter | ·015 |
| Diameter fore-and-aft of shaft at middle | ·018 |
The tibia ([Plate IX.], Fig. 3) is very long and heavy, with broad proximal articular face, the inner borders of which are prolonged upward and separated by a groove.
The shaft at the tuberosity is subtriangular, with strongly concave sides. The tuberosity is prominent, with a deep pit on its upper surface for the insertion of the ligament of the patella. The shaft below becomes sub-cylindrical, and decreases regularly in size downward. Its curvature is forward. The distal articular face is divided by a smooth ridge into two deep facets. The malleolus is long.
The fibula ([Plate IX.], Fig. 2) is distinct, straight, and very slender. The distal end is but slightly expanded, and is strongly marked by a vertical groove externally. The proximal end articulates with the overhanging portion of the proximal face of the tibia.
Measurements of Tibia.
TIBIA.