No. 433.] 



CERTAIN GROUPS OF BIRDS. 



35 



body and the characters of the long tail. It favors its reptiloid 

 organization too much, for it is probable that the typical species 

 of the genus Archaeopteryx were about seventy-five per cent 

 bird and but twenty-five per cent reptile. If the fossil remains 

 of the earlier ancestral stock of this group of forms are ever 

 discovered we will meet with types presenting just as much 

 of the reptile in their organization as bird, but they will not 

 have developed the feathers that Archaeopteryx possessed, nor 

 will the hind limbs be as ornithic in structure. Some of these 

 long-tailed reptiloid birds were about the size of a fish crow, 

 while others were much larger. As is well known, they had a 

 long, lizard-like tail composed of twenty-one vertebrae, and into 

 the skin that covered these were inserted twenty-one pairs of 

 conspicuously developed tail feathers, a pair to each vertebra. 

 Morphologically, these long and slender joints were distinctly 

 reptile in character, and doubtless had quite as much motion, 

 individually and collectively, as do the vertebrae in any of our 

 larger whip-tailed lizards of the present time. The compara- 

 tively small, pyramidal skull of these ancient forms was much 

 flattened above, with its occipital aspect truncated obliquely. 

 Either orbital cavity was large, and true teeth in grooves, or 

 sockets, armed either mandible. 



Reptilian characters largely predominated in the remainder 

 of the vertebral column of Archaeopteryx, for the articular sur- 

 faces of such of the vertebrae as have thus far been examined 

 and studied are flat, and the sacral ones were few in number. 



According to Marsh the sternum was represented by a single 

 broad plate of bone, and it is likely that it developed a keel. 

 The shoulder girdle was very birdlike, especially the os furcula. 

 Pycraft, who has examined all the fossil specimens of these 

 Jurassic birds, says : " The dorsal ribs have been described as 

 wanting uncinate processes ; an unsafe conclusion, since these 

 are often absent in the skeletons of existing birds, having been 

 lost in maceration. The cervical ribs appear to have been 

 much more slender than in modern birds, and to have remained 

 movably articulated throughout life. « Abdominal ribs,' resem- 

 bling rather those of the Crocodilia than of the Chameleonida, 

 appear to have been present." 



