OSTEOLOGY OF THE HYOPOTAMIDiE. 
39 
and the shape and position of the great trochanter. The shape of the femur in 
Hyopotamus (fig. 5) is remarkably uniform in its thickness, is exceedingly straight, and 
presents on its posterior surface, above the internal condyle, no deep pit for the plantaris 
muscle, but a simple rugosity, as in hogs. Some comparative anatomists seem to attach 
a great importance to this fossa, though I cannot do so, seeing that this fossa 
is developed or absent in animals belonging to both series, Paridigitata and Impari- 
digitata. For instance, it is very large in the Horse, but absent in the Rhinoceros ; 
developed in most Ruminants and Hippopotamus , but absent in Camelidce and Suidce , 
where we find, in place of the pit, a rugose surface for the attachment of the same 
muscle. 
The fore part of the distal extremity (Plate XXXV. fig. 2), as in most living Ungulates 
of both series, with the exception of the Suinse, Hyomoschus , and some Ruminants, has 
a more developed internal rotular edge, though the difference in thickness of the internal 
and the external edge is not carried to such a degree as in Bovidae and Horses, but is 
comparatively slight. The internal condyle is also a little thicker than the external. 
The lower extremity (Plate XXXV. fig. 2) of the femur from Hempstead may belong 
to Hyopotamus bovinus by size : this last specimen was kindly lent me by the Museum 
of Practical Geology in Jermyn Street ; it is figured of the natural size. 
Dimensions of the Femur of Hyopotamus. 
Puy. 
Hempstead. 
Hempstead (Plate XXXV. fig. 2). 
Length 
283 
? 
Transverse breadth of the upper broken end 
Antero-posterior depth 
.36 
Transverse breadth of the ' 
proximal extremity he- 
62 
47 
Transverse breadth of the distal end 
..61 
tween the articular head 
and the great trochanter . . _ 
Breadth of the rotular surface 
.26 
The Tibia (Plate XXXVI. fig. 7). — I had for the study of this bone two nearly entire 
specimens from Hordwell, belonging to the large didactyle form Hiplopus , and some 
incomplete upper and lower ends from Puy ; these last undoubtedly from the tetra- 
dactyle Hyopotamus , as no Hiplopus is found at Puy. The tibia of the Hiplopus from 
Hordwell approaches very nearly in length to that of a Reindeer, showing that the 
two-toed Hiplopus must have been very high on the hind legs, and the long metatarsals 
confirm this view. The general shape of this tibia is triangular from the upper 
part down to the distal extremity, and not so much rounded in the lower half as the 
tibia of the Suinae. The crista anterior is not very high, with only a slight patellar 
depression on its fore part, much shallower than in Pigs. The shaft of the whole 
bone is very straight ; the outer edge, facing the fibula, is exceedingly sharp, while the 
inner is more rounded. The distal end (fig. 7') shows a very rectangular outline, with 
two straight deep grooves for the upper pulley of the astragalus. The inner distal process 
of the tibia, or the so-called inner malleolus, which holds the astragalus from the inner 
side, is much longer than in Suina, approaching more to the size it exhibits in most 
Ruminants, with the exception of Tragulina , as these last have an exceedingly short 
