266 
PROFESSOR H. G. SEELEY OR THE STRUCTURE, ORGARIZATIOR, 
carried could not have been suspected without the evidence from the specimen 43,525. 
The distal epiphysis was quite as singular, for it comes away, leaving a concave 
surface on the shaft (Plate 23, figs. 2, 3), which has a sharp margin on the superior 
surface, and allows the epiphysis to extend for some distance proximally on what may 
be termed the inferior aspect of the shaft. In their well ossified character and large 
size, transverse separation from the shaft, and union with it in the adult, these 
epiphyses are unparalleled among Reptilia, and in all these respects are comparable 
to the similar ossifications in the long bones of Mammals. From the differences of 
proportion and form, the specimens 36,249 and 4-9,389 may be regarded as different 
species of the same genus, and provisionally referred to Dwynodon', but No. 43,525 
differs in ways which may well be generic. 
The specimen is 32 centims. long, and is a massive bone which terminates 
proximally in an olecranon process (Plate 22, fig. 1), which is larger than the 
expanded distal end, and helps to form the large obliquely concave articular surface 
for the humerus, which extends forward so as to widen the proximal end of the bone 
to about 22 centims., while the width of the distal end is 13 centims., and the least 
width of the shaft, at 10 centims. from the distal end, is 9'5 centims. 
The internal aspect of the bone is comparatively flat, being slightly concave in 
length and slightly convex transversely, with the proximal and distal borders slightly 
elevated. The impression on the upper part of the bone is the result of crushing. 
The anterior border between the proximal and distal articulations is 17 centims. 
long, straight in the middle, and becomes curved forward at each end towards the 
proximal and distal articular surface. 
The posterior contour of the shaft is concave at the distal end, but diverges back¬ 
ward as it extends proximally, and becomes a convex curve, which is continued on to 
the j^roximal surface of the olecranon. 
The bone is compressed from side to side, but a rounded ridge extends longitu¬ 
dinally down the middle of the external aspect of the bone, commencing at the 
anterior external corner of the proximal articular surface, and running distally and a 
little inward, widening as it goes, so that distally it only makes the bone tran.sversely 
convex, while proximally it divides the bone into two lateral portions, which meet 
each other at an angle. The posterior of these surfaces is about 26 centims. long, 
11 centims. wide proximally, and 7 centims. wide distally; flattened, but slightly 
concave in length, and at the proximal end slightly concave transversely. A narrow 
posterior area separates this lateral surface from the internal surface, towards which 
it approximates as it extends outward ; it is 5"5 centims. wide proximally, where it 
passes on to the proximal cartilaginous surface of the olecranon, but becomes narrower 
distally, and in the middle of the length the limiting angles of this surface, wliich 
looks obliquely outward, have disappeared, and the bone is transversely rounded. 
Distally, it is a groove margined by sharp short tul)ercles or ridges, defining a channel 
about 3 centims. wide. In Dicynodon this posterior area does not appear to exist. 
