HAPLODONTID2—LIMB BONES OF HAPLODON RUFUS. 5T9 
trochanteric tuberosities, without appreciable neck. There is a strong deltoid 
ridge, running down from the greater or external tuberosity. and terminating in 
a stout, prominent, roughened tubercle just above the middle of the shaft, from 
which a slighter ridge runs down to the inner side of the ulnar articular 
facet. Below, the bone flattens and widens laterally to a breadth of 0.60. 
From the external condyle, a sharp ridge curves backward and upward to 
subside, on the shaft at the middle of the latter; the inner condyle project- 
ing laterally much farther from the articular facet than the outer one, though 
no such condylar ridge is prolonged up the shaft of the bone. This condyle 
is perforated with a large canal, oval in section, formed by a bony trabecule 
thrown across in front. The ulnar portion of the articular facet, lying in the 
main axis of the bone, constitutes, as usual, a simple ginglymoid joint, being 
very convex antero-posteriorly,-concave in the opposite direction ; its inner 
edge is ridged, its outer continuous with the radial articular surface, which 
latter is convex in all directions. Just above the joint, at the back of the 
bone, there is the usual pit for the reception of a process of the ulna; but 
the bone is not here perforate, though very thin. The position of the articular 
surfaces allows strong flexion of the forearm, but scarcely permits complete 
extension. | 
The una, two inches or more long, presents a strong olecranon extend- 
ing back of the joint to a distance greater than the length of the articular 
surface. The latter is a semicircular nick, very oblique in position with refer- 
ence to the axis of the bone; the facet for the articulation of the radius is 
distinct. On its inner face, the shaft is deeply grooved for the reception of 
the radius, which lies in close apposition with the ulna for the whole of its 
own length; but the ulnar groove continues up beyond the head of the radius. 
On the inner face of the bone, a somewhat similar groove runs from the side 
of the olecranon past the joint, but soon becomes obsolete. The ulna ends 
below with a simple conical extremity, which takes but little share in the 
formation of the wrist-joint. 
The radius, about 1.60 long, lies close to the ulna its whole length; the 
shaft is much bent outward; the head is oval in section, with a cupped 
facet for humeral articulation, and smooth, convex, lateral facet for the ulnar 
joint. The tubercle for insertion of the biceps is recognizable. The lower 
extremity is enlarged, bearing an oval facet, the outer corner of which is 
produced as a slight process. Notwithstanding the restriction of motion 
