The Humerus ([Plate VII.], Fig. 1).—The humerus is short, but excessively stout, twisted slightly on its axis; it decreases gradually in size downward, with the smallest diameter about two inches below the end of the deltoid ridge. The head is large, hemispherical, and sessile, projecting very slightly out of the axis of its shaft. The great tuberosity is heavy, but not high, and is separated from the low lesser tuberosity by a shallow bicipital groove.
The trochleæ are very nearly equal in size, directed obliquely to the axis of the shaft, and are separated by a narrow groove, which runs from the supra-trochlear fossa down and in, then back and up to the anconeal fossa. The condylar tuberosities are large and rugose; the external is the greater, and is directed antero-posteriorly. The deltoid ridge is long and heavy, and extends nearly two thirds down the shaft, branching out into two forks near its end. The supinator ridge is short and rudimentary, differing in this respect entirely from the great development found on the humerus of the Proboscidea.
The supra-condylar fossa is small, subcircular in form, and very deep, it has the peculiarity of being placed above the external condyle alone. The anconeal fossa is median in position and quite deep.
Measurements of Humerus.
| M. | |
| Length | ·63 |
| Smallest circumference of shaft just below deltoid ridge | ·288 |
| Greatest proximal circumference below greater tuberosities | ·45 |
| Width of trochlea on anterior side | ·154 |
| Length of anconeal fossa | ·071 |
| Width of anconeal fossa | ·062 |
| Width of distal end at condylar tuberosities | ·23 |
| Length of deltoid ridge | ·22 |
| Length of groove running from supra-trochlear to anconeal fossa | ·272 |
The Ulna ([Plate VII.]. Fig. 2).—The ulna is long, heavy at both ends, with a slender trihedral shaft that curves forward, and decreases in size as it approaches the distal end. The proximal end has its articular face for the humerus divided into three facets, the vertical being long and extremely convex; the horizontal has the pre-axial face the longer. The olecranon is very massive and rugose, sending up on its external side a high, pointed projection; while on the internal side, the olecranon becomes compressed and projects inward; these tuberosities are separated by a wide, shallow groove for the tendon. The distal articular face is large, single, and is concave antero-posteriorly, and convex laterally. The styloid process is very heavy.
Measurements of Ulna.
| M. | |
| Length of sigmoid notch | ·089 |
| Width of sigmoid notch (horizontal face) | ·049 |
| Diameter of proximal end below articular face (fore-and-aft) | ·076 |
| Diameter of proximal end below articular face (transverse) | ·059 |
| Diameter of distal articular face (fore-and-aft) | ·061 |
| Diameter of distal articular face (transverse) | ·051 |
| Length of olecranon | ·112 |
Pelvis.—The ilia are greatly expanded laterally, with the iliac surface concave and the gluteal surface nearly flat; thin in the middle, they increase in thickness near the borders. The crests curve regularly, and project above and beyond the sacrum, but do not bend over the acetabula. The acetabular borders are only slightly concave; the prominence for the attachment of the rectus muscle (extensor) is low and V-shaped. The direct internal surfaces of the ilia, comprised between the pubic and ischiatic borders, become deeply concave below the ischiatic portion of the acetabulum. The sacral surfaces are wide and triangular in shape; above they project beyond the sacral spines.