Ok the Idextity of the Ascending Process of the Astragalus in Birds with 

 THE Intermedium. By Edward S. Morse. 



JpROM the time that Hermann Von Meyer, fifty years ago, first recognized that the 

 Triassic reptiles had characters which removed them widely from living forms, anato- 

 mists and palaeontologists have been diligently at work defining with greater exactness 

 the anatomical features of these early animals. The results of these labors have been to 

 increase the distinctions between these forms and their supposed living representatives, 

 and to erect for some of them new orders in the old class of Reptiles. Nor has this been 

 the only result ; through Professor Cope's (1, 2, 3) studies of the Dinosaurs of the Greensand 

 of New Jersey, avian affinities were pointed out which were subsequently and independently 

 confirmed by Professor Huxley (4, 5). 



With the gradual unfolding of these features, the unquestionable reptilian character of 

 the group with its unmistakable avian pelvis and hind limb became evident. 



The birds whose affinities with other classes had been so obscure as to have caused 

 them to be designated as a closed type, became better understood ; for the key to their 

 mysterious affinities was found in the rocks of the Mezozoic age, and in the transient 

 features of their own embryos. 



With the closer approximation of the Reptiles and Birds by Huxley, under the greater 

 division Sauropsida, our only wonder is that relationships so plain had never before been 

 recognized. Gegenbaur's (6) determination of the more important elements of the tarsus 

 in Birds, and the rapid growth of our knowledge of the Dinosaurians through the labors 

 of Leidy, Cope, Marsh and Huxley, have gradually strengthened the conviction that 

 among the Dinosaurs, or closely related forms, we were to look for the progenitors of the 

 present birds. 



Professor H. G. Seeley (7), in a lecture on the Dinosauria, delivered before the Scientific 

 Club of Vienna, while admitting for them a few avian characters, considers that some 

 relations have been overrated, and that the avian affinities of the Dinosaurians were not 

 so strong as had been supposed. It seems to me, however, that he does not give sufficient 

 importance to the fact that some of these relations have been based on the characters 

 presented by birds in an advanced stage of embryonic growth, that is to say in embryos 

 so far advanced, that all the leading avian features had been established. 



While Professor Seeley admits certain avian characters in the hind limbs of some 

 Dinosaurians, he says that they are limited to two points : " First, the development of a 

 strong anterior crest, which is directed forward and outward, so as to extend in front of 



