218 1 ON THE EXTINCT MAMMALIA OF 



sides of the radial articulation. The upper division is trapezoidal in outline, about 

 six inches, in its long diameter, obliquely crossing the fore part of the bone from 

 without inwardly and downward. The smaller division is sub-oval and about an inch 

 and a half in diameter; and it articulated with the inferior part of the external condyle 

 of the humerus. Both divisions of the humeral articulation are extended downward 

 for the articulation of the radius. The breadth of the two divisions together of the 

 radial articulation is about five and three-quarter inches. 



Two mutilated specimens of the upper extremity of the radius have nearly the 

 same form as in the Rhinoceros. The smaller specimen is five and a quarter inches 

 wide and three inches from before backward. 



Two specimens of the distal extremity of the radius measure severally six, and 

 seven and a half inches at their widest part. The carpal articular surface of the 

 smaller specimen in its perfect condition has been about five inches wide and two and 

 a half inches from before backward. 



Posterior extremities. — A small fragment of a hip bone has an acetabulum five 

 inches in diameter. 



Three mutilated upper extremities of the femur have the head averaging about 

 four and three-fourths of an inch in diameter. Another specimen has the head five 

 inches in diameter. In all, the head exhibits a large fossa for the attachment of a 

 terete ligament. 



A specimen of the lower end of a femur, nearly two feet in length, in the collection 

 of Prof. Hall, has a cylindroid shaft, somewhat compressed antero-posteriorly and 

 measuring at its narrowest part about nine inches in circumference. The shaft 

 exhibits no trace of a third trochanter, such as exists in many pachyderms. The 

 lower end of the bone measures about seven inches in breadth. 



An imperfect patella indicates a length of about five inches and a breadth of three 

 inches. Its form is ovoid, with the narrow end downward. The trochlear surface is 

 nearly equally divided by the usual carina, and the lateral facets are concave. 



Of three mutilated specimens of the proximal end of the tibia, the best preserved 

 exhibits a breadth of about six inches posteriorly, and the thickness, including the 

 tubercle for the ligament of the patella, is nearly as great. The two articular 

 surfaces are bounded behind by a wide shallow concavity. The outer one is 

 trapezoidal in outline, slightly concave transversely and convex antero-posteriorly. 

 The inner one is sub-oval and slightly concave. 



Of four specimens of the distal end of the tibia, the most perfect is four and a half 

 inches broad, and nearly resembles the corresponding part in the Rhinoceros. 



The number of toes possessed by Titanotherium I have not been able to ascertain. 



