DE. W. KOVALEVSKY ON THE 
0 A 
01 
In the humerus of Hyopotamus and Diplopus the middle Anoplotheroid bulging 
(Plate XXXVI. fig. 4, a) is much lowered, showing a step toward the condition seen in 
Pigs, in which it is raised into a very slight eminence. The inner margin of the humeral 
extremity (fig. 4, h) is produced a little downwards, but much less so than in Anoplo- 
therium. The supinator ridge is not prominent, though its rugose surface testifies to 
the attachment of strong muscles. There is a very large intercondyloid perforation (c), 
into which the olecranon entered deeply, as in modern wild hogs. The breadth of the 
articular surface is very great comparatively to the transverse diameter of the whole 
distal extremity of the humerus. The humerus figured in Plate XXXVI. fig. 4 belonged 
to the didactyle form, Dipl opus Aymardi ; it is from Hordwell : besides this humerus I 
had many specimens from Puy and Hempstead ; and as the two genera are confined to 
their respective localities, the Diplopus to Hordwell and the Hyopotamus to Puy and 
Hempstead, there is no danger of intermixing their fossil remains. The humeri of 
different size, which belonged to the tetradactyle Hyopotamus , are entirely similar to 
the one figured ; the only difference which may be noticed consists in the fact that the 
distal articular surface is relatively larger in the Diplopus than in Hyopotamus , as seen 
by the fact that in the three humeri of nearly equal size measured by me, the breadth of 
the articular surface is 42 millims. in Diplopus, and only 32 and 35 in two humeri of 
Hyopotamus. 
Dimensions of the Humerus. 
Diplopus 
Aymardi. 
(Eig. 4.) 
Hyopotamus. 
Hordwell. 
Hempstead. 
Puy. 
Largest transverse diameter of the distal extremity 
541 
55 
54 
Transverse breadth of the articular surface 
42 
35 
32 
Vertical height, articular surface, internal border (b) 
32 
31 
28 
Vertical height, articular surface, external border 
24 
23 
221 
Vertical height at the middle groove (a) 
23 
21 
20' 
Transverse diameter of the shaft (inf. 4) 
28 
22 
20 
Antero-posterior diameter 
39 
271 
The Ulna. — The antibrachium of Hyopotamidce consisted of two completely separate 
bones, and there is no trace of their having been immovably connected together, as in 
nearly all living Ungulates. I had several specimens of this bone from Puy, and from the 
English localities of Hempstead and Hordwell ; all, however, were more or less broken, 
save a splendid specimen from Hordwell in the British Museum. This right ulna (Plate 
XXXVI. fig. 1) fits the humerus figured in the same Plate (fig. 4) as exactly as if it came 
from the same individual. I will give the description of this complete specimen, and 
state the differences it presents from other ulna? from Puy ; the complete specimen figured 
in Plate XXXVI. belonged to the didactyle Diplopus. The shape of this bone in our 
didactyle genus is very striking from its extreme flatness and breadth ; it is much arched 
forwards, and this curvature reminds one of the ulna of Suina?. At the upper part we see a 
