244 



PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



Principal measurements of vertehrw — Contiuiiecl. 



THE CHEVRONS. 



1 



Chevrons from the anterior, middle, and posterior parts of the tail 

 were found in position with the caudals of Cat. No. 4282, U.S.N.M. 

 The anterior clievrons are longer than the spinous processes and 

 are reduced more slowly posteriorly. They 

 are Y-shaped, with expanded articular ends, 

 the surfaces of the opposite sides being 

 bridged across. Viewed laterally (see 1, 

 fig. 20), this end is av edge-shaped, the pos- 

 terior facet being the larger. The chev- 

 rons articulate intervertebrally with bev- 

 eled articular surfaces on the ends of the 

 centra. The opening between the branchas, 

 as compared with the chevrons of other 

 members of the Dinosauria. is much con- 

 stricted both transversely and longitudi- 

 nally. The free end is expanded and flat- 

 tened. The shaft is straight, not curved 

 backward, as in man}' reptiles, in this re- 

 spect similar to the anterior chevrons found 

 in the trachodonts. With the exception of 

 being smaller and having the articular end 

 about evenly divided between the anterior 

 and posterior facets, and the loAver part of 

 the shaft curved backward, the median 

 chevrons are very similar to those described above. 



Those of the more posterior region, however, are considerably 

 altered from the above types, as will be seen by reference to fig 19. 



Fig. 20. — (1) Antkiuok ciiEV- 



KON OF CAMPTOSAUKUS DIS- 



TAE Marsh. Cat. No. 

 5818, U.S.N.M. ; J nat. 

 size; side view; (2) pos- 



TEEIOR VIEW OF .SAME ; a, 

 ANTERIOR ; p, POSTERIOR. 



