342 THE HORSE. 
posteriorly, by two roughened projections. These form the lesser fetlock 
joint with the bone above. 
THE INFERIOR SURFACE resembles the corresponding part of the os 
suffraginis. 
Os Penis (the bone of the foot, formerly called the coffin-bone), In 
form it is semilunar, divided into wall, sole, articulatory surface, and 
retrossal processes, commonly called wings (see Fig. 31). 
THE WALL, the semicircular prominent part, possesses some degree of 
declivity, increasing in circumference from above, downwards. It is full 
of foramina, and rough. Superiorly, the bone bulges out, forming the 
coronal process (8, 8). The middle part of it terminates in a peak, whick 
looks slightly backwards—the cacumen coronee (the peak of the coronet). 
The wall terminates posteriorly in wings; THE RETROSSAL PROCESSES 
(10, 10); each wing is divided into two parts by a groove, which runs 
through it from before, backwards. 
THE INFERIOR SURFACE or SOLE is divided into an anterior semilunar 
plantar surface, and into a posterior sharp semicircular edge which divides 
it from the tendinous portion. The former is slightly concave, porous, 
and bounded by the inferior circumferent edge of the wall. 
THE SUPERIOR ARTICULATORY surface, semilunar in form, presents two 
lateral coneavities, separated by an eminence. ‘The eminence is bounded 
anteriorly by the cacumen coronx, which stands before it, the point 
looking backwards. Posteriorly, it is bevelled off for articulation with 
the os naviculare. 
Os NavicunarE (navis, a ship), sometimes called the shuttle-bone, in 
form is semilunar and elongated. It is divided into four surfaces and two 
extremities. 
THE SUPERIOR SURFACE presents, in its centre, an eminence, which 
declines laterally, leaving two slight concavities. 
THE INFERIOR SURFACE presents two shghtly convex divisions, with a 
prominent smooth ridge dividing them, running from behind forwards. 
THE ANTERIOR SURFACE presents superiorly a smooth triangular articu- 
latory surface, and inferiorly a porous, roughened face. 
THE POSTERIOR SURFACE is triangular, roughened, and porous. The 
extremities, the internal and external, turned upwards, terminate obtusely. 
THE PELVIS. 
THE GENERAL FEATURES belonging to the pelvis have been alluded to 
in the last chapter, and the sacrum which forms its upper wall has been 
described in this. It remains now to ascertain the shape and anatomical 
bearings of the bones which complete the arch. These in the embryo are 
three on each side, uniting below in the median line by symphysis, and 
above to the rough surface on the side of the sacrum. These three are 
Ist, Os ischi; 2d, Os alii, and 3d, Os pubis. The whole bone, which is 
firmly united in the adult, receives the somewhat Irish denomination of 
Us innominatum, or the unnamed bone. 
ON REFERRING TO THE SKELETON at page 308 it will be apparent that 
the attachment of this bone to the sacrum is so arranged that it shall act 
as a spring in breaking the jars received by the hind extremity from the 
ground. Its oblique direction, its comparatively short surface of attach- 
ment to the sacrum, and its own great length show this most plainly, 
especially when compared with the human pelvis, in which a very different 
