diagrams which are a vast improvement on my own, {758} and which are reproduced in Figs. 388ã393. Here we have, as extreme cases, the pelvis of Archaeopteryx, the most ancient of known birds, and that of Apatornis, one of the fossil ãtoothedã
birds from the North American Cretaceous formationsãa bird shewing some resemblance to the modern terns. The pelvis of Archaeopteryx is taken as our type, and referred accordingly to {759} Cartesian co-ordinates (Fig. 388); while the corôÙreôÙsponôÙding coordinates