100 LECTURES ON EVOLUTION m 



Hespcrornis and Ichthyornis have been discovered 

 have afforded no certain evidence of birds, with 

 the remarkable exception of the Solenhofen slates. 

 These so-called slates are composed of a fine 

 grained calcareous mud which has hardened into 

 lithographic stone, and in which organic remains 

 are almost as well preserved as they would be if 

 they had been imbedded in so much plaster of 

 Paris. They have yielded the Archceopteryx, the 

 existence of which was first made known by the 

 finding of a fossil feather, or rather of the impres- 

 sion of one. It is wonderful enough that such a 

 perishable thing as a feather, and nothing more, 

 should be discovered ; yet, for a long time, nothing 

 was known of this bird except its feather. But 

 by and by a solitary skeleton was discovered which 

 is now in the British Museum. The skull of this 

 solitary specimen is unfortunately wanting, and it 

 is therefore uncertain whether the Archceopteryx 

 possessed teeth or not. 1 But the remainder of the 

 skeleton is so well preserved as to leave no doubt 

 respecting the main features of the animal, which 

 are very singular. The feet are not only alto- 

 gether bird-like, but have the special characters of 

 the feet of perching birds, while the body had a 

 clothing of true feathers. Nevertheless, in some 

 other respects, Archceopteryx is unlike a bird and 

 like a reptile. There is a long tail composed of 



1 A second specimen, discovered in 1877, and at present in 

 the Berlin museum, shows an excellently preserved skull with 

 teeth ; and three digits, all terminated by claws, in the lore 

 limb. 1893. 



