SKELETON OF MARSUPIALIA. 351 



with the inferior, a, d, but recedes from it as it advances forward, 

 and then passes down, forming an obtuse angle, c, and with a gentle 

 concave curvature, to the neck of the scapula ; a small process ex- 

 tends from the middle of this curvature. 

 In the Potoroo, the upper costa is at first ^-"^ 



parallel with the lower, but this parallel 

 part is much shorter ; the remainder de- 

 scribes a sigmoid flexure as it approaches 

 the neck of the scapula. In the Great Kan- 

 garoo, the Perameles, Phalangers, Opos- 

 sums, and Dasyures, the whole upper costa 

 of the scapula describes a sigmoid curve, 

 the convex posterior position of which varies 

 as to its degree and extent. The sub- 

 scapular surface is remarkable in the Pera- 

 meles for its flatness, but presents a shal- scapuia of Koaia. 

 low groove near the inferior costa. In 

 most other Marsupials it is more or less convex or undulating. 



In the Kangaroos, fig. 211, the supraspinal fossa is of less ex- 

 tent than the space below the spine, and the spine is inclined 

 upward. In the Perameles and Dasyures the proportions of the 

 supra- and infra-spinal surfaces are reversed, and the whole spine 

 is bent downward over the infraspinal surface. In the Potoroos 

 and Phalangers the acromion is bent downward so as to pre- 

 sent a flattened surface to the observer ; in the Potoroos and 

 Opossums this appearance is produced by a true expansion of the 

 acromion. In the Perameles the coracoid process is merely re- 

 presented by a slight production of the superior part of the 

 glenoid cavity. In the Kangaroo and Potoroo it forms a protu- 

 berance on the upper part of the head of the scapula. In the 

 other Marsupials it assumes the character of a distinct process 

 from the same part, and attains its greatest developement in the 

 Wombat and Koala, in the latter of which it is forcibly curved 

 downward and inward, fig. 224, o. 



The clavicles are present in all the Marsupials, with the ex- 

 ception of the genus Perameles and probably also the Chceropus. 

 In the claviculate Marsupials they are relatively strongest and 

 longest in the burrowing Wombat, weakest and shortest in the 

 Great Kangaroo. In the latter they are simply curved with the 

 convexity forward, and measure only two inches m length. In 

 the Wombat they are upwards of three inches in length, and 

 have a double curvature ; they are expanded and obliquely trun- 

 cate at the sternal extremity, where the articular surface presents 



