356 BUREAU OF AMERICAN ETHNOLOGY [bull. 52 



trochlea describes an oblique line descending gradually in an inward 

 direction. As a consequence of this formation, the patellar trochlea 

 of the human femur is at its internal side considerably lower than at 

 its external, from which results that the patellar field appears as if 

 located obliquely with reference to the longitudinal axis of the body 

 of the bone. This is perhaps the greatest apparent difference between 

 the femur of Homo and that of Tetraprothomo. 



''However, to this difference must not be attributed more than a 

 relative value. This obliquity of the patellar trochlea is due to the 

 obhquity of the femurs of man, which incline, converging, from above 

 downward, and the tendon of the extensor muscle moves in the same 

 direction; as the patella is enveloped in the tendon mentioned, it is 

 obliged to move somewhat obliquely instead of in a perfectly vertical 

 direction, and it is the continuation of this oblique movement which 

 has produced in man the transverse broadening of the patellar troch- 

 lea and its obliquity inward. This is a characteristic exclusively 

 human, which has resulted from the biped progression in erect posi- 

 tion. . . . 



' ' But in the Tetraprothomo the biped and erect position was a char- 

 acteristic of quite recent acquisition, which as yet had not acted during 

 a sufficiently long time to be able to modify the form of this femoral 

 region; notwithstanding which, it can be stated that such a trans- 

 formation has already commenced. . . . 



''The femur of Tetraprothomo presents 1 cm. above the trochlea 

 quite a large suprapatellar fossa. . . . An equal fossa is seen in the 

 femur of the Homunculus, but it is located proportionately a little 

 farther above, besides which it is of smaller size and deeper. On 

 another femur from the superior Eocene from Patagonia, which I 

 attribute to the genus Anthropops, there exists an equal fossa but of a 

 larger size and located somewhat lower. It constitutes a species of 

 transition between that of Homunculus and that of Tetraprothomo, so 

 that it is seen that the latter has inherited this conformation from its 

 ancient predecessors of the superior Eocene, 



"The suprapatellar fossa is present also in many apes of the old 

 continent ; it is, however, located not only lower than in the apes of 

 the superior Eocene but also lower than in the Tetraprothomo. In the 

 femur of man the suprapatellar fossa has descended stUl lower, until 

 it has become located immediately above the superior border of the 

 trochlea, but it has augmented in extension and diminished in depth. 

 Furthermore, it has lost the subcircular or elliptic outline which it 

 had in the ancient forms, to assume a triangular contour. Still, in 

 the femur of the Man of Spy it is deeper [than in the present man] and 

 its triangular contour is less well defined. . . . 



"In the conformation of this region the Tetraprothomo occupies 

 evidently an intermediary position between man and the apes. 



