250 MEMOIRS OF THE CARNEGIE MUSEUM 
rib of the axis. Were the stump of the rib which remains attached to the axis in 
the Carnegie Museum, and which Mr. Hatcher has figured, removed, this smaller 
Fic. 21. Supposed rib of the axis of Diplodocus preserved in the American Museum of Natural History. The 
upper figure is an external view of the bone, the middle figure gives an internal view of the same bone, the lower fig- 
ure isan inferior view. 
rib might take its place and would undoubtedly articulate very neatly to the facet. 
In case the view entertained by the writer is correct, the form of the atlas and the 
axis with their attached ribs would be as given in the accompanying sketch (Fig. 
22) rather than as given in the figure which has been published by Mr. Hatcher. 
Such a location of these parts has in its favor the analogy of the crocodilian skeleton. 
Fic. 22. Sketch of the manner in which the two cervical ribs preserved in the American Museum of Natural His- 
tory may be supposed to have functioned in connection with the atlas and the axis. a, atlas; b, neural arch of atlas ; ¢, 
odontoid process; d, axis; e, rib of atlas; f, rib of axis; h, anterior process of rib of axis. 
The Cervical Vertebrex after the Axis. — Professor Marsh was undoubtedly in error 
in figuring as the cervical vertebra of Diplodocus the bone, an illustration of which 
is given in ‘“‘ Dinosaurs of North America,” Plate XX VI., Fig.3,and Plate XX VIL., 
