558 PEOrESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 



In both " innominata " the pubis (64) is broken off close to the acetabulum. The dia- 

 meters of the fractured surface are 2 inches 6 lines and ] inch 5 lines, the latter breadth 

 being near the back part of the bone which gives a subtriangular section. The anterior 

 apex is formed by a rough ridge, which rises from the haemal part of the pubis about 2 

 inches from the ilio-pubic process (Plate XLVII. fig. 1, e), leaving a shallow groove 

 between the ridge and the acetabular margin. 



The acetabulum (ib. fig. 4, t) is a nearly hemispherical depression, 5^ inches by 51- 

 inches across the opening, nearly 3 inches in depth; its rim is smoothly rounded 

 and less thick between the pubic ridge (64) and the " antero-inferior " iliac spine (d) ; 

 thicker and rough from this to the posterior or ischial part (ea') ; this, as it bounds the 

 acetabulum posteriorly, curves upward, gradually subsiding to form the outer wall of 

 the " cotyloid notch " or groove (_?/) conducting the vessels to the synovial and adipose 

 mass about the expanded, rough, slightly depressed surface for the origin of the " liga- 

 mentum teres." This surface (x) is oval, 2 inches 8 lines by 1 inch 3 lines in diameters ; 

 the cotyloid groove is 10 lines wide. The aspect of the acetabulum is outward and 

 more obliquely downward and backward than in Macropus, through a greater develop- 

 ment of the iliac, and especially of the pubic, walls. 



The sacrum is in the line of the lumbar vertebrse, upon which line the ilia are directed 

 obliquely forward and neurad at the angle above given (Plate L.). 



The condition already noted of the materials for the recomposition of the present 

 pelvis allows not of determination of the form and extent of the " brim of the pelvis," 

 assuming, as is most probable, that this was naturally entire ; nor does it give the extent, 

 form, and direction of the ischio-pubic symphysis which I conclude to have existed. The 

 transverse diameter of the pelvic cavity between the acetabular origins of the pubic bones 

 (ib. fig. 1, 64) is 1 foot, between the ischial spines [l, I) 7 inches. From the portion trace- 

 able of the " foramen ovale " I infer it to have been relatively large, as restored in Plate L. 



The ischia are divergent in the extent to which they are preserved. Although the 

 tuberosity and terminal part of the ischium are wanting, the hinder articular surface of 

 the second sacral centrum (Plate XLVII. fig. 2, s 2) permits a conclusion that the ischia 

 were free from any direct union with the vertebral column. 



The remains of no quadruped so large as that indicated by the above-described pelvis, 

 save those of Dij)rotodon, have been discovered in the freshwater deposits of Darling 

 Downs. Yet it would betray an undue confidence in the proportion of present acqui- 

 sitions of fossil remains to the entire extinct mammalian population of Australia, to 

 infer specific relationship from sameness of locality, or even some degree of juxtaposition 

 of parts of a skeleton. It is incumbent, therefore, to state the results of the comparison 

 of the pelvis in question with those of known genera of Mammals which have led me to 

 the conclusion that it is marsupial and referable to the largest known species of the 

 pouched order. 



The most conspicuous feature of the pelvis, without doubt, is unlike the corresponding 

 part in any known marsupial, and so much more resembles that in the Elephant as to 



