464 
PEOrESSOE OWEN ON THE DICYNODONT EEPTILIA. 
dislocation on the left side, has taken place where the suture with the pubis may origin- 
ally have existed ; but on the right side no trace of such suture is visible ; and the per- 
fect state of the surface of the pelvis at this part demonstrates as complete a confluence 
of the two bones, with each other and the ilium, to form a large ‘ os innominatum,’ as 
in mammals. 
The pubis (Plates XXIII. and XXIV. es) is remarkable for the bold and broad ante- 
rior convexity [h] of its iliac half, the inner part of which is perforated by an elliptical 
aperture (figs. I & 4,/“), answering to that in the pubis of the Monitor*. The outer 
part of the bone is produced into a short obtuse process (r), less developed proportionately 
than that in the Monitor’s pubis. Beyond this process the inferior border of the pubis 
bends downward and forward, rendering the antero-inferior surface of the half of the 
bone next the symphysis concave. The symphysis makes a slight angle near its begin- 
ning (Plate XXIII. fig. 1, y), projecting towards the pelvic cavity; the suture, there, is 
obliterated. The inferior or symphysial wall of the pelvis measures 14 inches across in 
a straight line from the border of one acetabulum to that of the other. The length of 
the symphysis {ih. fig. 2 , 63 , y, 64 ^ in a straight line cannot have been less than 8 inches ; 
but the upper or anterior margin is wanting [ib. fig. 1, es]. Its external contour is first 
concave, then convex, lengthwise. The broad, subquadrate ischio-pubic walls of the 
pelvis on each side the symphysis are slightly concave, outwardly, both vertically and 
transversely; the hinder three-fourths of these appear to have been formed by the 
ischium (et) : there is no ‘ obturator ’ space or vacuity, merely the outlet of the pubic per- 
foration appears externally. Both ischia and pubis combine to form a continuous tract 
of bone at the symphysis, which presents a thick protuberance at its lower or outer part 
near its termination (Plate XXIII. 64 ). The thick posterior border of the ischium is 
concave below the acetabulum, lengthwise, expanding into an angular tuberosity. 
The outlet of the pelvis (Plate XXIV. fig. 3) is of a semielliptic form, 9 inches in 
transverse and 4 inches in the fore-and-aft diameters. If the inlet or brim of the 
pelvis (Plate XXIII. fig. 1) be defined by the smooth thick convex border of the first 
sacral ribs (pZ), it presents an oval form, and measures 11 inches in transverse and 
10 inches in fore-and-aft diameters, the latter being taken from the middle of the fii’st 
sacral vertebra to the symphysis. 
From the study of the above-described most interesting portion of the dicjiiodont 
skeleton, we learn- — 
1st. That there were no lumbar vertebrae, e. none bearing the technical anatomical 
characters of such but that free ribs continued to be developed to the pelvic or sacral 
series. 
2nd. That the sacral series includes six vertebrae. 
3rd. That the ilium, ischium, and pubis coalesce into an ‘ os innominatum.’ 
* CrviEE, ‘ Ossemens Eossiles,’ pi. 17, fig. 39, 1. 
t This negative character is open to the same kind of objection as that relative to the ‘hippocampus 
minor ’ in animals below man. 
