XIV.] MARSUPIALIA. 237 



connection with the coracoid, and finally remains a mere 

 styliform, or slightly flattened process. 



The coracoid in both forms is unusually large, ossifies 

 ectosteally according to Parker, and has an epiphysis on its 

 free hook-like extremity. 



The clavicle {cl) of Choloepus is well developed, attached 

 externally to the loop of bone on the scapula, formed by the 

 united extremities of the acromion {a) and coracoid (<:), 

 and internally by the intervention of a long fibro-carti- 

 laginous " omosternum " (degenerating into a mere ligament 

 in the adult) to the presternum. In Bradypus the clavicle 

 is very small, and separated by a long interval from the 

 sternum. It originally articulates at its scapular end, as in 

 Choloipus ; but in consequence of the atrophy of the acro- 

 mion, it is left attached to the end of the coracoid, in which 

 unusual situation it remains through adult life. 



In the Marsupialia the scapula is tolerably uniform in 

 shape. The acromion is long, and the coracoid small, of a 

 somewhat hooked form, and thick at the base. It ossifies 

 by a separate endosteal nucleus. 



The clavicle is present in all known Marsupials except 

 the Bandicoots i^Peramelidce). It has always a " mesosca- 

 pular segment " at its outer end, and a " precoracoid seg- 

 ment " at its sternal end ; these are, however, not ossified. 

 Most generally it is attached to the acromion by a rather 

 strong ligament, but in the Wombat by a synovial articu- 

 lation. It is usually connected to the presternum by omo- 

 sternal cartilages of varying length, best developed in the 

 Didelphidce.. 



The shoulder girdle of the Monotremata (see Fig. 80) 

 differs widely, in many points, from that of any other 

 Mammal, and far more resembles that of the Lizards. 



The scapula is rather long and narrow, and (especially in 



