758 



THE THEOEY OF TRANSFORMATIONS 



[CH. 



and which are reproduced in Figs. 388 — 393., Here we have, as 

 extreme cases, the pelvis of Archaeopferyx, the most ancient of 

 known birds, and that of Apatornis, one of the fossil "toothed" 



I i I t, s- 6 7 B ij 



Fig. 390. The co-ordinate systems of Figs. 388 and 389. with three 

 intermediate systems interpolated. 



J 4 3- 6 7 y y 



Fig. 391. The first intermediate co-ordinate network, with its 

 corresponding inscribed pelvis. 



birds from the North American Cretaceous formations — a bird 

 shewing some resemblance to the modern terns. The pelvis of 

 Archaeopteryx is taken as our type, and referred accordingly to 



