Loc. cit., p. 110.
This is one of the most common fossils found in the Bridger Basin. We have numerous specimens, chiefly from Henry's Fork, exhibiting a large range of individual and sexual variation. As Dr. Leidy has already pointed out, the strength and depth of the lower jaw is extremely variable, increasing with the age of the animal; so that the most worn teeth are associated with the deepest jaws.
In addition to the jaws and teeth, (which have been very accurately described), we have a portion of a pelvis and femur, which are important as tending to confirm the reference of this genus to the Lemurs.
The pelvis is represented by the acetabulum and a small portion of ilium and ischium. They resemble the corresponding parts in the skeleton of Stenops gracilis. The acetabulum is a long oval, not subcircular, deep, and quite narrow from side to side. It appears to be directed nearly straight outwards. The ilium is narrow, has a concave gluteal surface, and a prominent acetabular border. The pubis evidently projected forward, making a right angle with the ilium; while the ischium is slender and nearly in the same plane with the ilium. The femur is thoroughly lemurine in shape. The shaft, (as much of it as is preserved), is straight and sub-cylindrical; it is not flattened even distally, but becomes very thick and trihedral in shape just above the trochlea. The trochlea is long, and rises obliquely upon the shaft; the groove is deep, and the two divisions are asymmetrical, the external somewhat the larger. The condyles are large. They are but slightly convex in either direction and project backwards, and are broadest posteriorly. The internal is the larger. They are separated by a deep but not wide popliteal groove, which does not extend into a popliteal fossa. The position and shape of the condyles are such as show that the femur must have been very oblique to the tibia, as in the other lemurs. The tuberosities, especially the internal, are very large and prominent. The whole distal end has an asymmetrical appearance, owing to the greater size of the internal condyle.
Measurements.
| M. | |
| Breadth of ilium at acetabulum | ·0065 |
| Vertical diameter of acetabulum | ·007 |
| Transverse diameter of acetabulum | ·009 |
| Fore-and-aft diameter of shaft of femur above trochlea | ·0065 |
| Transverse diameter of shaft above trochlea | ·0065 |
| Width of trochlea | ·004 |
| Length of trochlea | ·0075 |
| Breadth over condyles | ·010 |
| Breadth of inner condyles | ·005 |
OLIGOTOMUS, Cope.
Ann. Rep. U. S. Geol. Survey of the Terrs., 1872, p. 607.