548 
PROEESSOR OWEN ON THE EOSSIL MAMMALS OE AUSTRALIA. 
as in Marsupials and most Mammals, they vary in length, curvature, degree in which 
the groove for the intercostal vessels and nerve is excavated, distinction of head and 
tubercle, and relative position of the latter (Plate L. pi i-u). 
The longest specimen measures 2 feet 1 inch, following the convexity of its curve. 
The tubercle is low, 3| inches from the head ; the intercostal groove is shallow, and 
chiefly defined by a ridge-like production of the posterior border at the upper fourth of 
the rib, 3 or 4 inches in extent. Beyond this the rib loses thickness and gains breadth, 
the latter dimension reaching to 1| inch about one-third from the broken end. 
Another specimen presents a greater degree of curvature. The tubercle is better 
developed, has a more definite articular surface, extending upon the neck of the rib. 
The broadest part of the rib (1 inch 9 lines) is at the upper third of the bone. This rib 
had a more anterior position in the chest than the former ; the extent preserved, follow- 
ing the convexity of the curve, is 1 foot 6^ inches. 
A third specimen with head, tubercle, and intercostal groove well marked, is less 
curved than the former, and is larger than either of the above described. A length 
of 1 foot 4 inches is preserved. The fractured end is elliptic, 1 inch 9 lines in long 
diameter, 1 inch in short diameter ; but the rib midway between the end and the 
head attains a breadth of 2 inches. This has come from nearer the middle of the 
chest. 
The only entire specimen is a posterior rib, with the tuberosity relatively small and 
rough ; the head large, intercostal groove almost obsolete ; body of the rib straight 
along its distal half, which gradually expands, with loss of thickness to a breadth of 2 
inches 2 lines. The length of this rib, following the convex curve, is 1 foot 8 inches. 
The lower extremity shows the roughened surface for the attachment of the costal 
cartilage. 
The costal fragments yield little more than the character of size. The vertebral end 
of one, which includes the tubercle, has a circumference below that part of 3^ inches. 
Another fragment has a circumference of 4^ inches ; a third fragment is nearly 6 inches 
in circumference ; a fourth fragment shows a flatter shape. 
From the shortness of the costigerous vertebrae and the size of the ribs, their inter- 
spaces must have been narrow. 
Assuming with much confidence that the dorso-lumbar series in Diprotodon included 
nineteen vertebrae, I assign one more pair of ribs than in the Kangaroo, and reckon 
fourteen pairs in the dorsal series (Plate L.). 
§ 6. Scapula . — The scapula is represented in the Boydian collection of Diprotodont 
remains by an almost entire specimen of that of the left side (Plate XLV.), and by a 
fragment of the one of the right side. 
It is narrow in proportion to its length, and chiefly peculiar by the production of the 
subspinal plate anteriorly (ib. a), whereby the usual proportions of the triangular mam- 
malian scapula are reversed, the part answering to the base (ib. b) being the apex, and 
