488 PEOFESSOE OWEN ON THE SPECIES OP PHASCOLOMTS. 



The spine (e) beginning near the angle (b) of the base (d) rapidly gains in depth or breadth 

 as it approaches the neck (c), where the acromion (f, /') rises clear of the body of the 

 bone. The spine is thickest at the two ends and along its free border, which gradually 

 gains thickness as it bends downward to form the acromion (/'), where thickness 

 becomes breadth, the plane of the process being nearly at right angles with that of the 

 spine. 



The glenoid cavity ((/, and figs. 7, 8) is an irregular oval, with the small end upon the 

 base of the coracoid (h). The tubercular ridge (/, figs, o, 6) for the ' triceps longus ' 

 muscle is well marked ; it begins near the lower usually sharp border of the glenoid 

 cavity ; and a roughness may be traced from it along one third of the hind border (a). 

 The acromion {/,/') extending beyond the glenoid cavity, curves gently toward the 

 coracoid. This element, or process (/*), is short, thick, and inclines obliquely inward, or 

 toward the subscapular surface or aspect (figs. 2, 5). This surface is undulate. A lon- 

 gitudinal channel, parallel with the origin of the spine, is bounded by longitudinal con- 

 vexities, the upper one subsiding to a concavity at the antero-superior angle of the 

 quadrilateral, the lower one to a concavity along the hind border. The short straight 

 'base' (d) or 'vertebral border' of the scapula is thicker than either of the other borders 

 or ' costse,' and is thickest at the angles where it joins them, and which are rounded off. 

 The spine takes a more oblique course to the neck in Phascolomi/s platyrMnus (fig. 4) 

 than in Phascolomys latifrons (fig. 1) ; the body of the scapula is broader in proportion 

 to its length, and the glenoid cavity is narrower in proportion to its length in Phase. 

 platyrMnus. In Phase, latifrons I have noted a variety in which the antero-inferior 

 angle of the quadrilateral was more produced and the cervical emargination shorter and 

 deeper ; but usually the form of this part is nearly the same in both species. The hind 

 angle of the base is produced backward in Phase, latifrons (figs. 1 & 2, a) ; not so in 

 Phase, platyrhinus. The subscapular surface (figs. 2, 5, k) near the postsuperior angle 

 (5), for the attachment of part of the ' serratus magnus,' is defined by a stronger ridge 

 in Phascolomys latifrons (fig. 2) than in Phascolomys platyrMnus (fig. 5). 



I append the following dimensions : — 



Ph. latifrons^. Ph.platyrhinus'. 



in. lines. in. lines. 



Extreme length of the blade-bone 5 60 



Length of hind border (' external or axillary costa ') . , , 4 4 3 



Length of front border (' superior costa ') 3 1 3 5 



Length of base ('vertebral costa') 1 11 2 4 



From lower (cervical) angle of front border to end of coracoid 1 11' 2 5 



Breadth of the middle of the scapula 1 10 2 5 



The head of the humerus (PI. LXXII. figs. 1-4), especially the articular part [a), shows 



' PI. LX51. figs. 1-3. ■ Prom a larger individual than the suhject of PI. LXXI. figs 4-6. 



' In a second specimen it was 2 inches 2 lines. 



