Acheopteryx macrura. 4.4.1 
posterior angle of their junction is hollowed the articular 
cavity of the humerus, in which the scapula takes the greater 
share. 
Fig. 2. 
SE 
UZe= © 
co ; SS 
h NIA (= 
Ca ] m «4 
5 
GR 
& 
-Ua 
Fore-limb of Crocodile. 
If we were to suppose the scapule straight and elongated, 
sabre-shaped instead of triangular, and the narrow part of the 
sternum reduced to nothing, so that the two coracoids could 
meet in the median line, we should have the shoulder-girdle 
of Archeopteryx. 
Now the first of these conformations is realized in the Ptero- 
dactyls, where the scapulze are like those of Birds, while the 
sternum is widened in the shape of a shield (fig. 3). On the 
other hand the reduction of the sternum is found in the 
Ichthyosaurs and the Plesiosaurs. The scapula of these 
animals is long and straight, but directed vertically from below 
upwards, while that of Birds, of Pterosaurs, and of Arche- 
opteryz runs parallel to the vertebral column. On the other 
hand, in the Halosaurs the two coracoids meet by symphysis 
in the middie line; the sternum is wanting, but there is an 
episternum, which, in its turn, fails in Archeopteryx. The 
Ichthyosaur has clavicles, which are wanting in the Plesi- 
osaurs. 
I come, then, to the conclusion that the shoulder-girdle of 
Archaeopteryx is that of a Reptile, that the furcula and the 
sternum, widened into a buckler and bearing a keel (so cha- 
racteristic of all Birds except the Ratites), were completely 
wanting im it, and that the other bones, both im their com- 
