LIZARD-TAILED BIRDS. 
575 
general organisation Hesperornis approximated indeed very closely to the modern 
divers, with which it agrees in the general conformation of the skull and limb- 
hones, as well as of the pelvis. Whereas, however, the modern divers, have the 
long spike-like kneecap, or patella, united with the tibia, in the extinct bird 
these two bones remained distinct. In dimensions, Hesperornis was a bird of 
large size, attaining a height of rather more than a yard when in the upright 
position. That it was thoroughly aquatic in its habits is self-evident; while it 
may with considerable probability be regarded as a specialised and flightless 
offshoot from the ancestral stock of the modern divers; although this would 
not justify its inclusion in the same family as the latter. An apparently allied, 
although very imperfectly known type of bird ( Enaliornis ) is represented in 
England, where its remains have been obtained from a thin stratum lying at the 
base of the Chalk, known as the Cambridge greensand. 
Lizard-Tailed Descending lower in the geological series, and reaching those 
Birds. strata lying below the chalk, such as the Portland limestone, and 
known as the Jurassic series, we meet in certain Bavarian rocks, corresponding in 
age to those of Portland, with remains of birds departing much more widely from 
existing types than any hitherto mentioned. These birds, of which but a couple of 
imperfect skeletons, with impressions of the wing and tail-feathers, are known, are 
named Archaeopteryx, and constitute a group— Saururce, or lizard-tailed birds— 
regarded by some as of equivalent rank to the flying and flightless birds, but by 
others as of equal importance with the two together. In size these birds were 
about equal to rooks, with which they agree in being evidently adapted for perch¬ 
ing on the boughs of trees. In addition to the possession of a small number of 
conical teeth in the short jaws, they are characterised by having a long, lizard¬ 
like, tapering tail (which gives the name to the group), and from each joint of 
this a pair of feathers take origin. In this respect they differ from all the birds 
hitherto noticed, in the whole of which the bones of the tail are shortened, the tail- 
feathers arising in a fan-shaped manner from its terminal joint. In addition to 
this, they are further characterised by the first three metacarpal bones of the wing, 
as well as those representing the corresponding fingers, being perfectly distinct 
from one another, and each terminal joint of the latter being furnished with a 
well-developed claw; all other birds having the metacarpal bones, as well as some 
of those of the fingers, welded together; while there are, at most, but two claws 
(in the young of the seriema). It may be mentioned here that although the three- 
clawed digits in the wing of the lizard-tailed birds are commonly regarded as 
representing the first, second, and third of the typical five-fingered limb, Mr. C. H. 
Hurst believes that they really represent the second, third, and fourth; and he is 
thus led to conclude that the same will hold good for the digits in the wing of an 
ordinary bird. Be this as it may, in having cup-shaped articular surfaces to the 
bodies of the vertebrae, the lizard-tailed bird resembles the later Ichthyornis ; but 
it differs from all other members of the class in having the three bones constituting 
the pelvis perfectly distinct from one another (as in most reptiles), while in the 
leg the tibia and fibula are likewise separate. As regards the general structure of 
the wing and leg, these remarkable birds agree, however, with their modern allies; 
the foot having a complete cannon-bone, and but four toes, of which the first is 
