LIZARD-TAILED BIRDS. 



575 



general organisation Hesperomis approximated indeed very closely to the modern 

 divers, with which it agrees in the general conformation of the skull and limb- 

 bones, 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-TaUed 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 kno^vn, are 

 named Archoeopteryx, 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, tliey 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), Mdiilc 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 



