172 O. C. Marsh — Sates on Mesozoic Yertebrate Fossils. 



The fore limbs are unusually small in comparison with the 

 posterior, and the relative size of the two is shown on Plate II. 

 The scapular arch presents many points of interest. The 

 scapula is large, and so much curved that the axis of its shaft 

 is nearly parallel to the articular faces of its lower extremity, 

 (Plate II, figure 1, s). On the anterior margin, above the 

 articulation for the coracoid, is a strong protuberance, with 

 a well-defined facet, adapted to the support of the clavicle, if 

 such a bone were present. The coracoid is very small, and is 

 perforated by a large foramen (Plate II, figure 1, t ! ). The 

 two peculiar bones now generally regarded as belonging to the 

 sternum were separate, as shown in Plate III, figure 1. 



The humerus is comparatively short, and has a prominent 

 radial crest. The radius and ulna are much elongated, the 

 latter being longer than the humerus, and the radius about the 

 same length. The ulna has a prominent olecranon process, 

 and is a stouter bone than the radius. The carpal bones were 

 quite short, and appear to have been only imperfectly ossified. 

 The fore foot, or manus, was very long, and contained three 

 functional digits only. The first digit was rudimentary, the 

 second and third were nearly equal in length, the fourth was 

 shorter and less developed, and the fifth entirely wanting, as 

 shown in Plate II, figure 1. 



In the functional digits (II, III, IY), the phalanges are 

 elongate, thus materially lengthening the fore foot. The ter- 

 minal phalanges of these digits are broad and flat, showing 

 that they were covered with hoofs, and not with claws. The 

 limb as a whole was thus adapted to locomotion or support, 

 and not at all for prehension, although this might have been 

 expected from its small size and position. 



The elongation of the fore-arm and manus is a peculiar 

 feature, especially when taken in connection with the ungulate 

 phalanges. It may, perhaps, be explained by supposing that 

 the animal gradually assumed a more erect position until it 

 became essentially a biped, while the fore limbs retained in a 

 measure their primitive function, and did not become prehen- 

 sile, which was the case in some allied forms. 



The pelvis is shown in Plate II, figures 2 and 3, and has 

 already been described by the writer. Its most notable features 

 are seen in the pubis and ischium, the former having a very 

 large expanded prepubis, with the postpubis rudimentary, 

 while the shaft of the ischium is greatly elongated. 



The femur is long, and the shaft nearly straight. The great 

 trochanter is well developed, while the third trochanter is large 

 and near the middle of the shaft, as shown in Plate II, figure 

 2. The external condyle of the distal end is projected well 

 backward, indicating great freedom of motion at the knee. 



