656 PEOFESSOR OWm ON THE EOSSIL MAMMALS OE AUSTEALIA. 



and there the spine is 1 inch in thickness and 1 inch 7 lines in fore-and-aft extent. The 

 anterior orifice of the neural canal (Plate XLVII. fig. 3, n) is 3 inches 5 lines in transverse 

 diameter, but only 1 inch vertically between the centrum and summit of the neural arch ; 

 and this dimension is rather lessened at the middle of the canal by a slight rising along 

 that part of the neural surface of the centrum. A medial vertical ridge with a depression 

 on each side marks the fore part of the base of the thick neural spine (ns i,).* The frac- 

 tured base of the prezygapophysis (z) of the first sacral measures 2 inches 4 lines by 1 

 inch 5 lines. 



A partial ossification extends from the base of the neural spine of the first to that of 

 the second sacral (ib. fig. 2, 7is i & 2), bisecting a deep triangular depression, which, how- 

 ever, does not communicate with the neural canal ; a continuous ossification from the 

 first to the second sacral neural arch forms a smooth unbroken ceiling to the canal. 

 The posterior outlet of the neural canal (ib. n') of the second sacral is transversely extended, 

 3 inches 6 lines across, 10 lines in height on each side the mid rising of the centrum. 

 A greater proportion of the neural spine (ns 2) of the second sacral than of the first is 

 broken away ; the remaining base gives 1 inch 8 lines in fore-and-aft extent, 10 lines in 

 greatest breadth, which is at the hind part ; the fore part is ridged with a small depres- 

 sion on each side. The irregular ossification is continued from the median ridge to the 

 antecedent spine. 



Of both iha a large proportion has been preserved. The acetabular part (0) swells out 

 from the body of the bone, before (fig. 1) and behind (fig. 2), and developes a tuberosity 

 (d) oblong lengthwise, triangular transversely, at the upper or anterior part of the brim 

 of the cavity. In advance of the acetabulum the ilium contracts, especially from the 

 neural to the haemal aspect, or is depressed and lamelliform; but continues thickest 

 medially to form the junction with the sacrum, and contracts laterally to a smoothly 

 rounded concave margin (ib. figs. 1 & 2, n). About the sacro-iliac symphysis the medial 

 and anterior border, or " crista" of the ilium (c) contracts to a thickness of 1^ inch, and 

 where it is entire is convex and roughened. At the fore part of this symphysis is an oval 

 foramen, 1 inch by 9 lines in diameters (ib. fig. 3, /), the outlet of a canal communicating 

 with the capacious intervertebral canal. The free portion of the ilium is lamelliform, 

 arches outwardly, the thin outer or hinder border (n) describing a bold concave curve. 

 Save for two inches near the symphysis of the right ilium, the crista is broken away. 

 The haemal surface of the iliac plate (fig. 1, 62) is almost flat. Transversely, it is convex 

 one-third of the extent from the fractured margin (c), concave to the opposite outer 

 margin (a, n), both curves being feeble ; lengthwise it becomes concave toward the ace- 

 tabulum. The htemal tract {l^p) of the sacro-iliac symphysis forms a low broad smooth 

 convex ridge, enlarging and slightly rising as it approaches the acetabular part of the 

 ilium, but subsiding before this begins to expand ; this ridge, or tract, feebly represents 

 the " linea ileo-pectinalis." It seems to be suddenly resumed by a process [e] at the 

 junction of the iUum with the acetabular end of the pubis (e*). I infer, at least from its 

 being broken off on each side of this pelvis, that it projected far enough to be called 



