PROFESSOE OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 



551 



The total length of the above described scapula is 2 feet 3 inches ; the extreme breadth 

 is 1 foot 2 inches ; the long axis of the glenoid cavity is 6 inches, the short axis 4 inches 

 2 lines ; the height of the spine at the base of the acromion is 4 inches. 



Fragments of scapula, from the bed of the Condamine River, west of Moreton Bay, 

 Australia, in the Museum of the Royal College of Surgeons, placed with some doubt in 

 the series of Diprotodont remains in my ' Catalogue of Fossil Mammalia' (4to, 1845, 

 p. 298), can now be certainly referred to Biprotodon australis. One of these fragments 

 (no. 1471) includes 4 inches of the interior part of the origin of the spine. " The thick- 

 ness of the neck of the scapula is 2 inches 9 lines ; that of the base of the spine is 

 1 inch. The indication of the sudden rising of this thick spine from the plane of the 

 scapula distinguishes it from that bone in the Rhinoceros, and its thickness is greater 

 than in the largest Hippopotamus ; it is also relatively greater in comparison with the 

 neck of the scapula than in the Elephant" (p. 298). The specimen was thus differ- 

 entiated, in 1845, from all known Mammals of corresponding or approximate bulk, and 

 is now seen to conform in the particulars cited with the bladebone of Biprotodon. 



A portion of the glenoid cavity and neck of the scapula of a large Mammalian qua- 

 druped (no. 1472), from the same Australian deposits, shows similar dimensions to 

 those in the entire scapula of Biprotodon australis. 



§ 7. Humerus. — In Macropus the articular head of the humerus is subhemispherical, 

 looks a little backward as well as upward (the bone being held vertically), and overhangs 

 the back part of the shaft. The inner and outer tuberosities rise above the head, in 

 front of it. The inner tuberosity is thicker and shorter than the outer one, which ex- 

 tends ridge-like obliquely from without inward and forward where that end projects, 

 forming the outside of the deep groove, dividing it from the inner tuberosity ; the groove 

 expands and shallows as it descends, and is soon lost in the fore part of the shaft. 



The inner tuberosity is supported on a columnar development of the fore and inner 

 part of the shaft. From the fore end of the oblong outer tuberosity the " deltoid" ridge 

 extends halfway down the middle of the fore part of the shaft, being more or less pro- 

 minent in different species. In all the ridge attains its greatest breadth and prominence 

 at its lower part before its sudden subsidence. At the outer side of the shaft above the 

 developed termination of the deltoid ridge, projects a short, thick, longitudinal ridge, 

 with a rough obtuse surface. Thus the fore part of the upper half of the humerus is 

 divided into two facets, the inner one deepening upwards to the inter-tuberous or bici- 

 pital groove ; the outer one broader and flatter, between the outer and the deltoid 

 ridges. The back part of the upper half of the humerus is also, but less definitely, 

 divided into two longitudinal tracts ; the outer one flattened or slightly concave trans- 

 versely where bounded by the outer ridge ; the inner one gradually contracting, with 

 increased transverse convexity, to be continued into the ridge leading to the ento-condy- 

 loid tuberosity. The shaft of the humerus is more bent, with the concavity backward, 

 than usual ; the distal end not being turned forward in the degree which gives the ordi- 

 nary sigmoid shape to this bone in unguiculate mammals. 



MDCCCLXX. 4 F 



