Sinclair: typotheria of the santa cruz beds. 
55 
continued forward to the extremity of the large bicipital tubercle, as in 
Protypotherium. The coracoid process is scarcely indicated. 
No trace of a clavicle has been observed. 
The humerus (PI. VIII, fig. 7) is of about the same length as in 
Pachyrukhos , but may be readily identified, among other characters, by its 
larger head, stouter shaft, the greater transverse expansion of the distal 
end and the entire absence of an internal epicondylar foramen. The 
shaft is strongly curved antero-posteriorly, laterally compressed proximally 
and transversely expanded distally. The head is large, overhanging the 
shaft posteriorly. The tuberosities are not prominent, not exceeding the 
head in elevation. The deltoid ridge is broad and strong. Distally, the 
supinator ridge is not very well defined, resembling in this respect Pro- 
typotherium. The inner epicondyle is very heavy and the inner epicon- 
dylar foramen entirely wanting. The distal articular surface is similar to 
that of Protypotherium , with the exception that the inner lip of the trochlea 
is shorter, not so sharp and less completely separated from the inner 
epicondyle. A supratrochlear foramen is wanting. 
The radius and ulna are short and very heavy. The radial shaft (PI. 
VIII, fig. 10) is strongly arched antero-posteriorly and expanded trans- 
versely both proximally and distally. The head is oval in outline, its 
proximal surface concave externally for the humeral capitellum and 
flattened internally for contact with the inner lip of the trochlea. The 
articular surface for the ulna is convex transversely, plane proximo-distally, 
and evidently permitted considerable freedom of motion. The neck is 
constricted antero-posteriorly and expanded transversely. Distally, the 
radius is irregularly triangular in cross section, with a large oval concave 
facet for the scaphoid and lunar. The ulnar articulation is concealed in 
anterior view by a prominent flange on the outer margin of the distal end, 
proportionately larger than the similar structure in Protypotherium. The 
styloid process is short and the groove for the extensor tendons especially 
conspicuous and deep. 
The ulna (PI. VIII, fig. 9) exhibits the same decided lateral curvature 
as in Protypotherium , with strongly sigmoid posterior border. The 
olecranon is especially heavy, with the subcutaneous portion broad and 
almost flat and the area of insertion of the triceps quite rugose. The 
olecranon and coronoid processes have the same degree of anterior exten- 
sion. Distally, the shaft decreases greatly in weight and is transversely 
