DISTRIBUTION OF ORGANISMS. 21] 



only referable to struthious birds an equally early offshoot 

 from the aquatic order. Some few are more dubiously as- 

 signed 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 confirmation, little can be 

 founded uj)on this, more especially as a footprint 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 vulturine bird : soon after 

 which ornitholites, as they are called, become of greater 

 abundance ; and " here," says Mr. Strickland, " 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." 1 



Finally, we have to inquire into the connexions between the 

 lower vertebrate classes and the highest, the MAMMALIA. 

 Naturalists place the Birds between the Reptiles and Mam- 

 mals ; yet in some respects the birds are not truly inter- 

 mediate. 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 transitions from class to class, which in 

 general are the leaps of the development process, the passage 

 from reptile and bird to mammal is obscure ; only indicated 

 in a few stray facts. Perhaps the fossil blank at the conclu- 

 sion of the cretaceous era has helped to keep light from this 

 subject. Still we have enough to bear us out in saying, that, 

 as the fishes connect with reptiles, and these with birds, so do 

 reptiles and birds together connect with mammalia ; thus 

 placing the general fact of the continued advance of animal 

 life from its lowest to its highest point beyond a doubt. 



1 Report ou the Progress and Present State of Ornithology, by H. E. 

 Strickland; British Association, 1844. 



