4 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
extinct toothed bird Hesperornis, from the Cretaceous 
deposits of North America, for the elucidation of which 
we are indebted to the labours of Prof. Marsh. In this, 
as in the other types to be considered, attention will be 
chiefly concentrated on the fore-limb, pectoral-girdle, and 
sternum. 
Hesperornis regalis, the type of the genus, was a huge 
bird, measuring from the point of the bill to the end of 
the toes about 6 feet, and was eminently adapted by 
the manner of development of its posterior extremities for 
an aquatic life. It had a long beak, and teeth of a 
definitely reptilian form inserted in continuous grooves. 
In general form it resembled a Diver (Colymbus), and it 
agreed with that bird and the Grebes in its long, narrow 
pelvis, large cnemial crest of the tibia, and relatively 
enormous patella; and it 1s now generally considered to 
have had its nearest allies in these birds. On the other 
hand, it has many points of contact with the Struthious 
birds, with which it was classed by its discoverer, and 
described by him as ‘‘A swimming Ostrich.” There are 
characters in the skull, such as the fact that the upper 
articular head of the quadrate bone is not divided into two 
distinct facets, which point in this direction, but the most 
striking resemblances are, perhaps, to be found in the 
sternum and shoulder-girdle. The sternum was com- 
pletely smooth, and devoid of all trace of a keel. The 
coracoid was short and wide, and it and the scapula were 
nearly in the same straight line, thus much resembling 
the condition found in the Ratites; but these two bones 
were not ankylosed together as they are in the group of 
birds just named, and, moreover, there were two separate 
clavicles. The fore-limb indicates almost the greatest 
amount of degeneration of any known bird, as it is repre- 
sented by the humerus only. The remaining bones of the 
