418 



ZOOLOGY 



SECT. 



The differences between the two avian sub-classes, the Arcliseor- 

 uithes and the Neonithes, are, however, of a far more fundamental 

 nature ; and as Archaeopteryx, the sole representative of the first of 

 these groups, is a unique form, and perhaps the best example of 

 an undoubted link between two classes Reptiles and Birds it. 

 will be convenient to deal with it separately. 



Sub-Class I, Archaeornithes. 



Only two specimens of Archceopteryx litkographica have hitherto 

 been found, both in the finely-grained lithographic limestone of 



FIG. 1056. Archaeopteryx lithographica. From the Berlin specimen, c. carpal ; d, 

 furcula ; co. coracoid ; h. hunierus ; r, radius ; sc. scapula ; u. ulna ; I IV, digits. 



