SIVATHERIUM GIGANTEUM. 253 



to be formed of large cells, with the diploe expanded into plates, 

 and the outer and inner laminae wide apart. This character 

 is very marked at its upper margin, where its cells appear to 

 join on with those of the frontal. The condyles are very 

 large and fortunately very perfect in the fossil (Plate XX. fig. 1) ; 

 the longest diameter of each is 4'4 inches, and the distance 

 measured across the foramen magnum from their outer angles 

 is 7*4 inches — dimensions exceeding those of the elephant. 

 Theu' form is exactly as in the Ruminantia, viz. their outer 

 surface composed of two convexities meeting at a rounded 

 angle : one in the line of the long axis, stretching obliquely 

 backwards from the anterior border of the foramen magnum ; 

 the other forwards and upwards from the posterior margin, 

 their line of commissure being in the direction of the transverse 

 diameter of the foramen. The latter is also of large size, its 

 antero-posterior diameter being 2-3 inches and the transverse 

 diameter 2*6 inches. The large dimensions of the foramen and 

 condyles must entail a corresponding development in the verte- 

 brse, and modify the form of the neck and anterior extremities. 



The sphenoidal bone, and all the parts along the base of 

 the skull, from the occipital foramen to the palal:e, are either 

 removed or so concealed by stone as to give no characters for 

 description. 



The part of the brow from which the nasal bones com- 

 mence is not distinguishable. The suture connecting them 

 with the frontal is completely obliterated, and it is not 

 seen whether they run up into a sinus in that bone or 

 how they join on with it. Between the horns there is a rise 

 in the brow, which sinks again a little forward. A short way 

 in advance of a line connecting the anterior angles of the 

 orbits there is another rise in the brow. From this point, 

 which may be considered their base, the nasal bones com- 

 mence ascending from the plane of the brow at a considerable 

 angle. They are broad and well arched at their base and 

 proceed forward with a convex outline, getting rapidly nar- 

 rower, to terminate in a point curved downwards, which 

 overhangs the external nostrils. For a considerable part of 

 their length they are joined to the maxillaries ; but forwards 

 from the point where they commence narrowing, their lower 

 edge is free and separated from the maxillaries by a wide 

 sinus, so that viewed in lateral profile their form very much 

 resembles the upper mandible of a hawk, detached from the 

 lower. Unluckily in the fossil, the anterior margins of the 

 maxillaries are mutilated, so that the exact length of the 

 nasal bone that was free from connection with them cannot 

 be determined. As the fossil stands, about four inches of the 

 lower edge of the nasals, measured along the curve, are free. 



