Osteology o/Aramus scolopaceus. 
47 
practically 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 the windings 
Fig. 3. 
A. Front view of the keel of Aramus. 
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 austral asiana, it is less 
in G. carunculata, and 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 depression just below the small 
spina externa, which is most evidently a vestige, and that 
* * The Natural History of the Cranes ' (London, 1881), p. 81. 
