A FOSSIL REPTILE. 741 
surface is interrupted by the notch which forms the glenoid 
cavity. The posterior part of this is formed by the coracoid, 
which articulates with the scapula and precoracoid, and extends 
backwards behind them for a long distance. 
The glenoid cavity thus formed by all three bones looks almost 
directly outwards and is essentially a trihedral pit; it must have 
been covered during life by a thick pad of cartilage, but can never 
have shown any trace of the screw-shape shown in early Coty- 
losaurs such as Diadectes, Labidosaurus, and, to a less extent, 
“ Pariasaurus.” . 
Text-figure 4. 
Procolophon trigoniceps, 6. 
A. Right lateral aspect of shoulder-girdle.  X 1. 
A’. Ventral aspect of shoulder-girdle. X 1. 
B. Ventral aspect of shoulder-girdle, and abdominal ribs. X 1. 
C. Right side of pelvis from outside. 1. 
The so-called notch in the precoracoid proves when fully 
exposed to be really a foramen passing through the bone and 
opening on its upper surface. Its most remarkable feature is 
the strong rounded ridge which forms its anterior border on the 
lower surface. 
The clavicles are large bones, beginning at the upper margin 
of the scapula; they run down the whole anterior border of that 
bone and then turn suddenly in, being vertically expanded and 
applied to the anterior face of the T-shaped interclavicle. 
The humerus of Procolophon is a very remarkable bone. The 
