DISTRIBUTION OF AVES IN TIME. 469 



lately, tolerably certain that these impressions were formed by 

 Birds. We must not, however, lose sight of the possibility 

 that these impressions may have been formed by Reptiles 

 more bird-like in their characters than any of the living forms 

 with which we are acquainted. The recent researches of 

 Huxley, Cope, and others, go to show that the Dinosaurian 

 Reptiles possessed the power of walking temporarily or per- 

 manently on the hind-legs, and many curious affinities to the 

 true Birds have been pointed out. It is therefore by no 

 means impossible that these footprints of the Connecticut 

 valley are truly Reptilian. 



The size and other characters of the above-mentioned im 

 pressions vary much, and they have certainly been produced 

 by several different animals. In the largest hitherto discov- 

 ered, each footprint is twenty-two inches long, and twelve 

 inches wide, showing that the feet were four times as large as 

 those of the African Ostrich. The animal, therefore, which 

 produced these impressions whether Avian or Reptilian 

 must have been of gigantic size. 



The first unmistakable remains of a bird have been found 

 in the Solenhofen Slates of Bavaria, of the age of the Upper 

 Oolites. A single unique specimen, consisting of bones and 

 feathers, but unfortunately without the skull, is all that has 

 hitherto been discovered ; and it has been named the Archcz- 

 opteryx macrura. The characters of this singular and aberrant 

 bird, which alone constitutes the order Saurura, have been 

 already given, and need not be repeated here. 



Other doubtful remains of birds have been alleged to occur 

 in the Mesozoic series, but many of these certainly belong in 

 reality to Pterodactyles. 



In the Tertiary Rocks, however, there are, comparatively 

 speaking, many remains of birds. In the Eocene Rocks of 

 France has been found a large bird, as big as an Ostrich, the 

 so-called Gastornis Parisiensis ; and in England, in the same 

 formation, we have a small Vulture (Lithornis vulturinus], and 

 a King-fisher (Halcyornis toliapicus). In the Eocene of Claris 

 in Switzerland occurs, also, the oldest known Insessorial or 

 Passerine bird, the Protornis Glarisiensis, which was about as 

 big as a lark. 



Numerous remains of birds have likewise been found in the 

 Miocene and Pliocene deposits. With the exception, how- 

 ever, of the Mesozoic Archaopteryx^ by far the most remark- 

 able remains of birds have been found in the Post-tertiary or 

 Pleistocene deposits. All the remains now alluded to are 

 those of gigantic wingless birds ; and it is worthy of notice 



