On Lost Forms between Birds and Reptiles. 3G 1 



However, the very fine calcareous mud of the ancient Oolitic sea- 

 bottom which has now hardened into the famous Lithographic slate of 

 Solenhofen, and has preserved innumerable delicate organisms of the 

 existence of which we should otherwise have been, in all probability, 

 totally ignorant, in 1861 revealed the impression of a feather to the 

 famous palaeontologist, Herman von Meyer. Von Meyer named the 

 unknown bird to which this feather belonged Arcliceopteryx liiho- 

 graphica, and in the same year, the independent discovery by Dr. 

 Hiiberlein of the precious skeleton of the ArcJioeopteryx itself, which 

 now adorns the British Museum,^ demonstrated the chief characters 

 of this very early bird. But it must be remembered that this feather 

 and this imperfect skeleton are the sole remains of birds which have 

 yet been obtained in all that great series of formations known as 

 Wealden and Oolite, which partly lie above, partly below, and partly 

 correspond with, the Solenhofen slates. 



Though some palaeontologists may be forced by a sense of con- 

 sistency to declare that the class of birds was created in the sole 

 person of Archceopteryx during the deposition of the Solenhofen 

 slates, and disappeared during the Wealden, to be re-created in the 

 Greensand, to vanish once more during the Cretaceous epoch and re- 

 appear in the Tertiaries, I incline to the hypothesis that many birds 

 besides Archoeopteryx existed throughout all this period of time, and 

 that we know nothing about them, simpl}'- because we do not happen 

 to have hit upon those deposits in which their remains are preserved. 



Now, what is this Archceopteryx like ? Unfortunately, the skull is 

 lost, but the leg and foot, the pelvis, the shoulder-girdle, and the 

 feathers, so far as their structure can be made out, are completely 

 those of existing ordinary birds. 



On the other hand, the tail is very long, and more like that of a 

 reptile than that of a bird in this respect. Two digits of the manus 

 have curved claws, much stronger than those of any existing bird ; 

 and, to all appearance, the metacarpal bones are quite free and dis- 

 united. 



Thus it is a matter of fact that, in certain particulars, the oldest 

 known bird does exhibit a closer approximation to reptilian structure 

 than any modern bird. 



Are any fossil reptiles more bird-like than those which now 

 exist? 



As in the case of birds, the Tertiary formations yield no trace of 

 reptiles which depart from the type of the existing groups. But 

 otherwise than is true of birds, the newest of the Mesozoic forma- 

 tions, the Chalk, makes us acquainted with reptiles which, at first 

 sight, seem to approach birds in a very marked manner. These are 

 those flying reptiles, the Pterodactyles, which resemble the great 

 majority of birds in the presence of air-cavities in their bones, in 

 the wonderfully bird-like aspect of their coracoid and scapula, and 

 in their broad sternum with its median crest. Furthermore, in some 

 of the Pterodactyles, the premaxillae and the symphysial part of the 



^ The fossil has been described hj Professor Owen in the " Philosophical Trans- 

 actions " for 1863. 



VOL. V. — -\o. L. 24 



