490 



KNOVS/'LEDGE • 



[April 7, 1882. 



I 



which liki'wino nroso from sockets ii» tht- jaws. In so 

 far a.H lIcsjMTornis is coiic«'nicd, it removes tiic liird class, 

 on thi' fiuc of thiiiRs, a sU-p ncnrcr to the ri'j(til(! hosts. 

 Koniierlv. part of the natiirulist's delinition of a liinl was 

 inchulol in thtMliiiaratioii that teitli were wanting. Now, 

 tlie ilelinition requires 8tret<-iiinK, to inciii(l<' a chariu-ter 

 wliiili is sliured in hy ccrtjiin reptiles. Just as otliers, npn- 

 seiited hv thu tortoises ami turtles, imitate the toothless 

 condition of existinj; birds. 



Hut the Ichthyornis of the chalk is even a more re- 

 markal'le Inrd fossil than Hesperornis. For the teeth of 

 the former are implanted in distinct sockets, whilst its 

 hn-asthone liad a keel, and its wings are of large size, and 

 indicate the jwsseftsion of liird-haMts, united to structures of 

 reptilian kind. But more pei'ulirir still, as a departure 

 from liird-characters was the nature of its vertehra- or the 

 joints of the spine : for Ichthyornis possessed vertebra', 

 which, like those of the fishes and of extinct reptiles, were 

 hollow at either end. Such a feature must naturally be 

 ninde much of in (•stiniatiii-; the relationship of this old 

 bird to the reptilian hosts. The size of Ichthyornis was 

 that of a pigeon. 



Preceding tlieso birds in time conies the Archcopteriix, of 

 the I'ppcr Oolite deposits of Solenhofen, in Bavaria. Here 

 the reptile-characters increase in number as becomes the 

 older nature of their possessor. A recently-procured speci- 

 men of this bird enabled a zoological authority to declare 

 that it was certainly not wholly a bird, and as certainly 

 not wholly reptile in its nature, but a strict link between 

 these classes. For, firstly, it has the tail of a lizard, 

 that is, the tail is long and jointed, and has no 

 plough-share bone, as in other birds (Fig. 5, B, h). 

 Secondly, the bones of its palm were not joined 

 together as in all other birds, whilst at least two 

 of its fingers appear to have been provided with claws, 

 a feature of exact reptilian nature. Then it likewise 

 lias been ascertained, by the discovery of the recent 

 s]>ecimen already referred to, that this old bird of the 

 Oolite possessed teeth. Judged fairly, then, Archa>optery.x 

 is, at the very least, as much a reptile as a Ijird. Its 

 shoulder and fore-limb (or wing) arc decidedly those of a 

 reptile, whilst its hind limbs are bird-like in nature. The 

 facts that such a race of animals once existed, and that 

 they livid at a period when, presumably, the bird-race was 

 undergoing its evolution from the reptilian confines, 

 may, in the eyes of any unprejudiced thinker, serve as 

 clear evidences that the common origin of birds and 

 reptiles is matter, not of speculation, but of scientific 

 demonstration. 



I have shown, thus, cursorily, the evidences supporting 

 the contention that if, standing within the bird-class, we 

 look for reptilian features within its limits, we are not dis- 

 appointed in our search. But on the reptilian side of things, 

 there are also evidences to be found of the community of 

 type from which the birds and reptiles of to-day have 

 sprung. It takes but a slight acquaintance with 

 zoology to discover that the curious lizard, Hattiria 

 (or Sftliftwdon), of New Zealand, as befits the curious 

 history of its native country, brings us face to face 

 with characters of abnormal kind, from the reptilian view 

 of matters at least For this lizard has ribs which are 

 decidedly those of bird-type, and, moreover, it has the 

 same lioUow-ended vertebra* seen in the fossil bird Ich- 

 thyornis. In other points of its structure as well, 

 JIatteria seems to rejiresent a primitive type of reptile, 

 presumably indicating that stage in the evolution of the 

 two classes wherein certain characters of the bird had 

 already liegun to be developed in the common ancestors 

 of these groups. 



The (lying reptiles (J'trn>il,iri,/I„) (Fig. 2) of the Lias, 

 Oolite, and Chalk, teach us tliat as the pure reptile thus 

 acquired powers of flight, the development of flight in 

 the bird-stock, which was evolved from the rej>tile, or 

 conjointly with it, need cause us no surj)rise. 



The Pterodactyls j)0.sse.s8ed tlie outermost finger (seen in 

 the illustration) enormously elongated, and adapted to 

 form the chief siijiport of a wing-membrane which ex- 

 tended along the sides of the body and between the hind 

 limbs and tail also, as shown in B, Fig. 2. It may Ijc 

 added that these reptiles had a keel on the breastlxine like 

 most living and e.xtinct birds, and whilst in some species, 

 the teeth were developed, in othei-s the jaws appear to 

 have been toothless, and to have been sheathed in 

 horn like those of bird.s. But these reptiles are not 

 '•links." They stand, not between liirds and reptiles, 

 but at the end of their own side-branch of the great tree 

 of animal life. Still, from the reptile-side, it may lastly 

 lie shown that the " found links " connecting them with 

 birds — it may be, of course, in different lines from those 

 indicated by Arch:eoptery.\ and its neighbours — already 

 find a place in the geological museum. In those curious 

 reptiles, of which Coiiipsiit/nat/ntii (Fig. 3) is the best known 

 example, the characters of birds and reptiles were united 

 in a literally surprising degree. Imagine a reptile posses- 

 sing a swan-like neck, with toothed and bird-like jaws: 

 suppose, further, that this animal had very rudimentary 

 front limbs, and that it walked on its two hind limbs like 

 a bird, and we may conceive that this Compsognathus, had 

 it been feathered, would have at least appeared to resemVjle 

 a bird much more nearly than a reptile. But a still 

 stronger piece of evidence in favour of its bird-relationship 

 awaits the naturalist when he discovers that the hind 

 limbs of these curious reptiles are, in respect of structure, 

 midway and between those of birds and reptiles. If we 

 examine the hind limb of a bird (Fig. 4, A), we notice that 

 the upper half of the ankle (As. Ca.) unites with the shin- 

 bone, or leg (T) : and as the lower half of the ankle joins 

 the instep ( 1 ), the ankle joint thus exists in the middle of 

 the ankle-bones, and the lower ankle aiid instep-bones form 

 a single bone (ni) bj- their union. In Fig. 5 the hind limb 

 of the Iiird is also seen, e being the single bone formed by 

 the union of ankle and instep-bones. In the reptiles limb 

 (C), the ankle-joint, as a rule, opens between the divided 

 ankle-bones; but the instep-bones (C ; L, ii., iii., iv.) are 

 not united either to one another, or to the neighbouring 

 ankle-bones. Now it is extremely interesting to discover 

 that the hind-limb of Compsognathus and its allies (B) is 

 exactly intermediate between birds and reptiles. Here, 

 the leg bones resemble those of birds in shape. The chief 

 ankle bone (As.) exactly corresponds with that of a bird : 

 and, as in birds, this bone lieconies united to the lower end 

 of the leg. But, lastly, as if to show the intermediate 

 nature of the lindi, the instep-bone (I — iv) remain free, 

 and the leg of Compsognathus is thus practically half- 

 way between that of the bird and reptile. Thus, as 

 in birds, the upper part of the ankle is unitetl to the leg; 

 but, unlike birds and like reptiles, the Compsognathus had 

 the lower part of the ankle free, and not united with the 

 instep. In a word, the hind limb of this old reptile re- 

 sembles the condition of the limb in the chick before 

 hatching, and it may thus represent that stage in the 

 evolution of the bird-type wherein the type of limb common 

 to the primitive stock was being gradually modified into 

 the more consolidated limb of the bird. 



Thus to-day, there exists a scries of forms, detached and 

 isolated, perhaps, but still eloquent enough in their de- 

 claration of the existence in past epochs of animals which 

 belong to no one class as defined by us to-day, and which 



