Osteology of Aramiis scolopaceus. 



47 



j)ractically absent. In my specimen, as will be seen from 

 the figure, there is a very small, but still very distinct, spina 

 externa which lies in the proper position for such a process 

 and may be compared with the admittedly present spina 

 externa of the sternum of Balearica ; these facts may be 

 readily gathered from an inspection and comparison of the 

 two figures submitted herewith (fig. 3, A & B). Now, in 

 other Cranes this spina externa is large, but it bears a 

 relation to the amount of complication shown in thewindingji 



Fio:. 3. 



A. Front view of the keel of Aravius. 



B. „ „ Balearica. 



of the trachea in those birds, where the tracheal loops may 

 excavate the front end of the sternum ; for example, the 

 spina externa is very large in Grus australasiana, it is less 

 in G. carunculata, aud very small in Balearica, which, as 

 a matter of fact, has not got a looped trachea. Associated 

 with the looped trachea is the excavation of the front of the 

 sternum, which is well known. Now it is highly interesting 

 to note that in Balearica, as pointed out by Mr. Tegetmeier'^, 

 there is a small but deepish depressiou just below the small 

 spina externa, Avhich is most evidently a vestige, and that 

 * ' The Natural History of the Cranes ' (London, 1881), p. 81, 



