418 



ZOOLOCJY 



SECT. 



Tlie differences between the two avian sub-classes, the Archa-or- 

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

 nature ; and as Areh;eopteryx, the sole representative of the first of 

 these groups, is a unicjue 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 oi Archa'opteryx lithocjrapliica have hitherto 

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



Fio. 1056.— Archaeopteryx litbographica. Fmin the Herliii specimen, o. carpal ; d. 

 furculu ; co. curacoid ; h. humerus ; ?•. radius ; sc, scapula ; i«, ulna ; 1— IV, digits. 



