48 



UNITED STATES NATIONAL MUSEUM. 



from the first to the fifth, the latter equaling the length of the twentieth of tlie 



series, and in this diameter exceeding all others. 



The first two or three centra might be called platycoelian, though they soon 



pass into the biconcave type, which continues throughout the dorsal series. The 



median cervicals have a much deeper concave 

 posterior end than the anterior end, but back of the 

 eighth the concavities of these ends become about 

 subequal. 



Viewed fiom below the ends are expanded, the 

 sides of the centra are pinched together, thus 

 making them concave longitudinally, with a strong 

 angular keel which widens at either end (fig. 16), 

 more especially the anterior, which is roughened 

 by coarse longitudinal striae. Proceeding toward 

 FRONT VIET, d, DiAPOPHYsts; B, NEURAL i^Q dorsols thc kecl bccomcs progressively less 



CANAL; p, PAEAPOPHTSIS; S, NEURAL SPINE; ^, j , . i. o 



ANTEEIOE ZYGAPOPHYSIS; z', POSTERIOR ZYGA- and ICSS COUSpiCUOUS. 



popHYsis. After Marsh. ^]j ^f .j^j^g cervicals have capitular f acets on the 



sides near the anterior end, as shown in figures 15 and 17,^. Well-developed dia- 

 pophyses extend outward from the sides of the neurapophyses. These have 

 heavy, expanded, articular ends, which look more downward than outward. The 

 diapophyses gradually increase in length proceeding posteriorly. On the side of 

 the centra near the posterior end, on a level with the parapophyses,is a roughened 



Fig. 15.— Median cervical vertebra of 

 Stegosaurus ungulatus Marsh. J Nat. 

 SIZE, a. Side view, i. Same vertebra, 



Fig. 16.— Articulated cervical vertebrae of Stegosaurus stenops Marsh. Cat. no. 4934, U.S.N.M. Type. J Nat. 

 size. Inferior view, a, Atlas; ax, axis; b, articular facet for cervical ribs;c3,c<,c5,c«, cervicals three to six; 

 PjPakapophyses; r', left cervical rib to atlas; r", left cervical rib to axis; r, articulated cervical ribs belong- 

 ing TO the fifth and sixth cervical vertebrae; z', posterior zygapophyses. 



protuberance wiiich probably indicates the point of insertion of ligaments. 

 These projections are especially pronounced on the cervicals of the posterior liaM * 

 of the neck. The neural canal remains large throughout the cervicals, changing 

 from a pear-shaped outline in the anterior ones to nearly circular openings in the 

 posterior members 



