HADROSAURUS. gj 



The abutments of the vertebral arch present a slight successive increase in width. 

 In the first specimen it is twenty lines wide ; in .the tenth specimen twenty-two 

 lines. 



The articular processes are like those of the precedmg caudal vertebree, and suc- 

 cessively increase their distance apart Thus in the second specimen of the series 

 under consideration the space reachmg from those anterior to the ones posterior 

 measures forty-six linQS ; in the third specimen the same space occupies forty-eight 

 lines ; and in the tenth, fifty lines. 



The spinous process, preserved entire in the third specimen (Fig. 13), is eight 

 inches and a half long. Directed upward and backward it is at first cylindrical, 

 but approaching its free extremity becomes laterally compressed. Judging from 

 the rernains of this process in the other caudal vertebrae, it has had a similar form 

 throughout. 



The transverse processes are apparently aU broken or bruised at the ends in the 

 vertebrse in which they have existed. In the six specimens in advance they appear 

 to have been formed as distinct elements, and were apparently coossified by a 

 broadly expanded root to the conjunction of the vertebral body and arch. In the 

 anterior tAvo specimens (Figs. 11, 12) they appear to have been short, robust promi- 

 nences, with their root extending nearly as far down as the middle of the side of 

 the body. In the succeeding three (Fig. 13) specimens the processes appear to 

 have been short, obtuse prominences, not reaching by their expanded root below 

 the upper third of the side of the body. In the next three of the series, as seen 

 in Figs. 14, 15, the transverse processes are obsolete, or appear as a slight, rough- 

 ened prominence, at or below the union of the vertebral body and arch. In the 

 last specimen no trace of the process appears, as seen in Fig. 16. 



The remaining five caudal vertebrae of the collection, of which the back four 

 are represented in Figs. 17-20, possess the same general form of the body as in the 

 preceding specimens, and exhibit a successive diminution of depth and breadth in 

 relation with the length, which also undergoes a moderate reduction. Thus in the 

 first of the specimens the body is nearly of equal length, depth, and width, their 

 measurements being about three inches. The body of the succeeding three speci- 

 mens (Figs. 17-19), which are nearly equal in size, is thirty-three lines long, twenty- 

 eight wide, and twenty-five deep. The last specimen (Fig. 20) has its body thirty 

 lines long, and twenty-one wide and deep. 



In the first of this series the spinal canal is vertically oval, eight lines high, and 

 six wide ; in the fourth specimen it is subcircukr, five lines and a half wide and 

 high. 



The abutments of the vertebral arch in the first specimen are twenty lines wide; 

 in the fourth specimen, thirteen lines. 



Transverse processes appear not to have existed in these five caudal vertebrae, as 

 no trace of them is visible. The vertebral arch in all is too much mutilated to 

 ascertain whether it was provided with articular and transverse processes. 



All the vertebrae I have described appear to be fully grown, their arch being 

 firmly coossified with the body. The sutural conjunction between the two arts 



11 April, 1865. 



