456 NATURAL SCIENCE. June, 1894. 



And even the highly-specialised and pre-eminently arboreal Passeres 

 are evolving terrestrial forms in the Larks, waders in the Wagtails, 

 and even waterfowl in the Dippers — none of which have as yet had 

 time to lose the typical foot of their order ; and thus avian history is 

 repeating itself. 



It would seem, therefore, that this highest group of birds is, in 

 virtue of its habitat and foot -structure, in reality one of the most 

 primitive. And this is paralleled among the Mammalia by the 

 pentadactylous condition of the otherwise highly-organised Primates. 

 If, then, as I hope, I have given reason to believe that the 

 arboreally-adaptcd form of foot is the one we should naturally expect 

 to find in the ancestors of the birds, this feature gives, I think, an 

 additional claim to Archceoptevyx to be regarded as one of those 

 ancestors, rather than as a side-branch of the avian tree. 



Its teeth, the free and clawed digits of its hands, and its long 

 tail without pygostyle, fulfil the requirements of a schematic primitive 

 bird, and if its grasping feet may be added to the design, we may 

 fairly say that in the Solenhofen fossils we have a creature which 

 stands as nearly as possible upon the central line of avian develop- 

 ment in past ages. 



Frank Finn. 



