221 



and with the olecranon not quite entire; it is a strong but low trihedral process, smooth 

 and concave on the inner side, roughish and flattened behind ; with a smooth almost 

 horizontal triangular surface at the upper part. The breadth of the base of the ole- 

 cranon is 3 inches 10 lines; the circumference of the base is 13 inches. The articular 

 surface answering to the " greater sigmoid cavity " is concave, longer and deeper from 

 before backward than from side to side. From its upper and outer part a less concave 

 articular surface is continued upon the inner side of the base of the olecranon. The 

 lower part of this surface, which may have afforded the " lesser sigmoid cavity " to the 

 radius, is broken away. The rough tract for syndesmotic junction with the radius (ib. 54) 

 extends down the outer side of the shaft inclining obliquely forward : it is about an inch 

 in breadth. There is a small but well-marked tuberosity and depression, on the outer 

 or radial side of the ulna, 1^ inch below the "greater sigmoid cavity," answering to a 

 corresponding process in the Wombat. The elongation of the olecranon in that bur- 

 rowing Marsupial, augmenting the lever for working the fore paw, does not exist, and 

 was not needed in the gigantic gradatorial Diprotodon. The portion of ulna above 

 described indicates a massive and powerful fore arm, and has encouraged me to indicate 

 the continuation of the ulna, as a distinct bone, to the carpus, in my restoration of Dipro- 

 todon (Plate XXXV.). The canal for the medullary artery enters the bone on the 

 inner side (that next the radius) below the "sigmoid" articular cavity, and the canal is 

 directed inward and a little upward. This fossil was obtained in the bed of the 

 Condamine River, west of Moreton Bay, by Sir Thomas Mitchell, C.B. 



§ 8. Pelvis. — In a collection of bones from fluviatile freshwater deposits at Eton Vale, 

 Darling Downs*, in the usual massive or weighty, semipetrified condition of fossils from 

 those beds, were fragments of a large pelvis, readjustible to the extent of giving a great 

 part of the sacrum and ilia, both ace tabula, the acetabular portion of each ischium to 

 the extent of 7 or 8 inches, and about 5 inches of the acetabular end of each pubis. 



The sacrum consists of two vertebrae (Plate XXXII. s 1, #2), uniting with the ilia 

 (ib. 62) by a terminal expanse of the transverse processes (ib. fig. pi 2), coequal with 

 the antero-posterior extent of the entire sacrum, and giving to that bone a subquadrate 

 form one-third broader than it is long. Much of the anterior articular surface of the 

 body of the first sacral (fig. 1, s 1) is preserved, and a smaller proportion of the posterior 

 surface of that of the second sacral (ib. s 2). Both surfaces show the usual mammalian 

 flatness and concentric lineation for union by intervertebral sclerous substance with 

 contiguous centrums : the rougher surface shows the loss of the epiphysial plate. The 

 transverse diameter of the fore part of the first centrum is 5 inches ; the vertical (neuro- 

 hsemal) diameter is 3 inches. The transverse diameter of the hind end of this centrum, 

 giving that of the fore end of the succeeding anchylosed centrum (s 2), is 3 inches 5 lines. 

 The ha?malf surface of both centrums (Plate XXXII. fig. 1, s 1, 2) is flat, subquadrate, the 



* These fossils, collected in the above-named locality by Edward S. Hill, Esq., were liberally presented to 

 the British Museum by Sir Daniel Cooper, Bart., in 1864. 



t In noting the position and aspect of the parts of this pelvis according to anthropotomical description, 



