sternum resembles that of the ornithorhynchis paradoxus, 31 
EXPLANATION OF THE PLATES. 
Plate II. 
Contains two figures; the first represents the different 
parts that compose the sternum, in the fossil animal, and 
their connection with the neighbouring bones ; the second the 
corresponding bones in the ornithorhynchus paradoxus; to 
show their resemblance. 
Fig. 1. The sternum, and bones connected with it, in the- 
animal whose bones are found in a fossil state. 
aa Two flat bones peculiar to the sternum of this animal 
and the ornithorhynchus. 
b A flat bone behind which is concealed the union of the 
edges of the two flat bones just mentioned. 
cc Two processes from this bone, by means of which it is 
united to the scapulas. 
dd The two scapulas, which, united to the flat bones, form 
the glenoidal cavities of the shoulder joints. 
eee A slender curved bone crossing the upper end of the 
sternum, and uniting the two scapulas together. 
ff The two first bones of the pectoral fin or paddle. 
Fig. 2. The sternum and scapulae in the ornithorhynchus 
paradoxus. 
aa Two flat bones nearly similar to those in Fig. 1. united 
to the scapulae, but making no part of the glenoidal cavity 
of the joint of the shoulder. 
b The bone corresponding to that marked b, Fig. 1. 
cc Two processes similar to those in Fig. 1. 
