Description of the Bones of a new Fossil Animal. 75 



The other humerus of the smaller individual measures eighteen 

 inches in length, and is not so perfect at the condyles. 



Cubitus. — This is a short, thick, and strong bone, the marks 

 for the attachments of the muscles being equally pronounced as 

 those on the humerus ; the present bone however belonged to 

 the opposite or left side, and to another and smaller individual. 

 The most remarkable peculiarity of this cubitus consists in the 

 size and form of the superior articulating surface, and of the ole- 

 cranon process ; the latter is broad and long, projecting upwards 

 and nearly in a line with the axis of the bone, the superior ante- 

 rior angle looking inwards, unlike the same parts in the mega- 

 therium and megalonyx. The radio-humeral articulating surface 

 of this bone consists also of two distinct facets or surfaces ; the 

 internal is much the highest and largest, is concave in its longest 

 or antero-posterior diameter, being nearly four and a half inches 

 long by two and a half inches wide. The posterior portion of 

 this surface is continued downwards and inwards, to form the 

 internal, smaller, and more concave facet ; this again is continued 

 at its anterior border into an irregular triangular disk, horizontal 

 to the shaft, for the accommodation of the proximal head of the 

 radius. These irregular surfaces are neatly adapted to the cor- 

 responding surfaces of the humerus, and, together with the ole- 

 cranon process, occupy about two thirds of the whole bone, as 

 will be perceived by the measurements below. The upper line 

 or rim of the shaft of this bone descends from the strongly pro- 

 nounced coronoid process, and ascends from the posterior superior 

 end of the olecranon, rendering the ulna somewhat triangular 

 in form, diminishing in size towards the carpal joint ; the shaft 

 is strongly compressed and deeply scalloped its whole exterior 

 side, with two deep depressions on its interior surface for the 

 lodgment of its powerful muscles. The carpal articulating sur- 

 face of this bone is nearly circular and somewhat convex ; the 

 disk for articulation with the superior head of the radius, is on 

 the inner surface of the ulna ; the larger oblong disk for the 

 lower head of the radius is on the anterior portion of the ulna, 

 so that the hand would remain in the state of pronation, still 

 enjoying some liberty of motion. Vide Plate I, figs. 9 and 10 — 

 a view of the proximal extremity. 



Dimensions of the cubitus : — total length, 16 inches ; distance 

 from the coronoid process to the inferior extremity of the bone, 



