DISTRIBUTION OF ORGANISMS. 191 



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of the scansorial or zygodactyle form of the foot, the outer 

 toe being turned completely behind. 



In the stone record there are, as is well known, few entries 

 of birds ; but such as there are bear a general correspond- 

 ence with this view of the genealogy of the class. The 

 Connecticut footsteps chiefly point to tribes which stand early 

 in the pedigree, namely, species allied in structure to the 

 snipes and plovers. Others, from their gigantic size, have 

 been thought only referable to struthious birds an equally 

 early offshoot from the aquatic order. Some few are more 

 dubiously assigned to rasorial birds. With regard to the 

 absence, here or at an earlier period, of swimming birds, let 

 it be considered that the phenomena are extremely local and 

 limited ; also, that the spot investigated is a portion of an 

 ancient shore, a haunt of wading rather than of swimming 

 birds. Recently, indeed, it has been announced that one of 

 the birds indicated by the footmarks was a swimming bird 

 a fulica, or coot ; but, as all such announcements require con- 

 firmation, little can be founded upon this, more especially as 

 a foot print resembling that of a finch was spoken of at the 

 same time. In rocks posterior to the Connecticut footmarks, 

 but within the secondary formation, occur three bird fossils, 

 one referred to the snipe family, another to the albatross, and 

 the third to the swallow ; the majority being thus applicable 

 to early portions of the genealogy. When we at length come 

 into the tertiary formation, we find, in the eocene, a vulte- 

 rine bird ; soon after which ornitholites, as they are called, 

 become of greater abundance ; and " here," says Mr. Strick- 

 land, " as in every other department of the animal kingdom, 

 we perceive a rapid approximation to the fauna, which is 

 characteristic of the period in which we live." ( 7S ) 



Finally, we have to inquire into the connexions between 

 the MAMMALIA and the lower vertebrate classes. Naturalists 

 place the Birds between the Reptiles and Mammals ; yet in 

 some respects the birds are not truly intermediate. We are 

 the less to be surprised on finding that the principal mammal 

 orders appear to be immediately connected with the Reptiles, 

 while only the lowest come through the birds. As usual in 



