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PROFESSOR H. O. SEELEY OR THE STRUCTURE, ORG/IHIZATIOR, 
specimens is in contact with the basi-sphenoid. I am not aware of any circumstance 
which would account for the absence of the missing bones, except an original delicacy 
of texture or absence of ossification, which favoured their removal; but such conditions 
are not found in any larger skulls. It might, however, be characteristic of young- 
individuals, and indicate this skull to belong to a young animal, but the form of the 
head is that of a new species. 
The Occipital Plate. (Plate 10, figs. 1,2.) 
There exists in the British Museum a detached occipital plate from a Dicynodont 
li 
skull, which is registered as ai^d appears to belong to an undescribed species. It 
is about 8 centims. wide by 6‘5 centims. high, thin and rounded on the contour of 
the upper half, and thicker and notched on the lower half. The plate is flattened on 
the posterior aspect (fig. 1), but more convex on the anterior face (fig. 2). The 
greatest antero-posterior measurement through the occipital condyle is 3 centims. The 
condyle is remarkable for its large size, subquadrate form, slight posterior extension 
beyond the surrounding bone, and subcentral position upon the occipital plate. It 
measures 2‘5 centims. wide, over the ex-occipital elements, which are subtriangular or 
subovate convexities, and make the wide upper part of the condyle, the lower part being- 
made by the basi-occipital, which has an unusually large condylar surface, 2 centims. 
wide, and transversely ovate. The vertical depth of the condyle is 1‘6 centira. Its 
contour is concave superiorly at the foramen magnum, with a parallel convex inferior 
margin, and small lateral concavities between the ex-occipital and basi-occipital 
elements. Its ex-occipital extension posteriorly does not exceed 6 millims., while that 
of the basi-occipital is only half as much. There is a saddle-shaped concavity on the 
inferior margin of the plate below the basi-occipital; it is concave from side to side, 
convex from behind forward and downward, and partly divides the two hyp-apophyses 
below the occipital region, which are here shorter than usual. These processes are 
convex from side to side, and I'S centim. wide. A delicate line descends down the 
middle of eacli process, coming from the outer side of the basi-occipital portion of the 
condyle, and this line I regard as the suture between the basi-occipital and ex-occipital 
bones. The width of the basi-occipital at the inferior termination of these diverging 
sutures is 2-7 centims. External to the ex-occipital element in the condyle, and hidden 
beneath its transverse expansion, is the usual perforation for the vagus nerve, which 
extends obliquely inward and upward. 
Tlie middle part of the occipital plate appears to be formed by the ex-occipital bones. 
The foramen magnum is I'Z centim. high, and El centim. wide at the base, -with the 
sides converging slightly upward, and arcliing together above. At 6 millims. above 
the floor of the foramen on each side, a delicate suture diverges outAvard and upward. 
I regard it as separating the supra-occipital and ex-occipital. The outwaard extremities 
of the sutures are 8 centims. apart, so that this is the width of the supra-occipital. 
