140 



and Phalangers the acromion is, as it were, bent do\ATi\vards, so as to 

 present a flattened surface to tlie observer. In the Potoroos and 

 Opossums this appearance is produced by a true expansion of the 

 acromion. In the Perameles the caracoid process is merely repre- 

 sented by a slight production of the superior part of the glenoid ca- 

 vity. In the Kangaroo and Potoroos it foims a protuberance on 

 the upper part of the head of the scapula. In the other Marsupiata 

 it assumes the character of a distinct process from the šame jjart ; 

 and attains its greatest development in the Wombat and Koala, in 

 the latter of which it is forcibly cur\'ed do\vnwards and inwards. 



" The humerus in the Dasyures and Tijylacine resembles that of the 

 dog-tribe, in the imperforate condition bf the inner condyle, but dif- 

 fers in the more marked development of the muscular ridges, espe- 

 ciaUy that which extends upwards from the outer condyle, for the 

 origin of the great supinator. This ridge is terminated abruptly by 

 the smooth tract for the passage of the musculo-spiral nerve. In 

 Phal. Cookii the intemal condyle is imperforate, and in Petmiriis 

 Sciureus it'v^ deej^ly notched ; but in other Phalangers andPetaurists, 

 as also in all the other genera of Marsupials, the internal condyle 

 of the humerus is perforated. 



" ITie ridge above the external condyle is much developed in the 

 Petaurus macrurus and P. sciureus, and notched at its upper part ; 

 there is the šame structure in Phal. Vuljnna, but it does not exist 

 iu Phal. Cookii. I find similar diiFerences in the development of 

 the supinator or outer ridge in the genus Perameles ; in the Per. 

 lagotis it is bounded above by a groove ; in Per. grisea it is less 

 developed and less defined. In the Kangaroos, Potoroos, \Vombat 

 and Koala, the outer condyloid ridge extends in the form of a 

 liooked process above the groove of the radial nerve. In all these, 

 and especially in the Wombat, the deltoid process of the humerus is 

 strongly developed ; it is continued from the external tuberosity 

 down the upper half of the humerus ; except in the Petaurists, 

 \vhere, from the greater relative length of the humerus, it is limited 

 to the upper third. The interspace of the condyles is occasionaliy 

 perforated, as in the Perameles lacjotis and Wombat. The articular 

 surfaces at both extremities of tlie humerus have the usual form ; 

 but it may be observcd, that in some Marsupials, as the Koala, the 

 external convexity at the distal articulation for the radius has a 

 greater relative extent than usual, and the ulnar concavity is less deep. 



" The bones of the fore-arm present little to detain our notice. 

 They are ahvays distinct and \velI-developed, and their adaptation 

 to pronation and supination is complete. The prehensile faculty 

 and unguiculate structure of the anterior extremities appear to have 

 been indispensable to animals requiring to perform various manipu- 

 lations in relation to the ceconomyof the Marsupial pouch, and when 

 such ananimal is destined, likę the Ruminant, to range the ■vvilderness 

 in quest of pasturage, the reąuisite 2)0wers of the anterior members are 

 retained and secured to it by an enormous development of the hinder 

 extremities, to vvhich the function of locomotion is almost restricted. 



" We find, therefore, that the bones of the fore arm of the Kangaroo 

 difter little from those of the burro-\ving Wombat, the climbing 



