marsh.] RRONTOSAURUS. 169 



The coracoid approaches more nearly that of Apatosaurus, which is 

 subquadrate in outline. In PI. XXII the scapula and coracoid of the 

 present species are placed nearly in the same plane, and the space 

 between them probably represents about the amount of cartilage which 

 originally separated them. Both scapula? were found in apposition with 

 their respective coracoids. 



The two sternal bones lay side by side between the two coracoids, 

 and in this plate they are represented nearly as found. They are sub- 

 oval in outline, concave above, and convex below. They are parial, 

 and when in position nearly or quite meet on the median line. Each 

 bone is considerably thickened in front, and shows a distinct facet for 

 union with the coracoid. The posterior end is thin and irregular. The 

 sternal ribs represented in figs. 12-15, p. 171, were found near the sternal 

 bones. The sternum of a young ostrich is shown for comparison on PI. 

 XXII, fig. 3. 



THE CERVICAL VEUTEBR.-E. 



The cervical vertebra? of the present species are quite numerous, 

 thirteen at least belonging in this part of the column. All are strongly 

 opisthoccelian. The anterior cervicals are very small in comparison 

 with those near the dorsal region. From the third vertebra to the mid- 

 dle of the neck the centra increase in length and especially in bulk, 

 but the posterior cervicals gradually become shorter. In PI. XX, figs. 

 3 and 4, the sixth cervical is represented, and this is typical for the 

 anterior half of the neck. All the anterior cervicals have coossified 

 ribs, as in birds. In the posterior cervicals the ribs occasionally become 

 free (PI. XXI, fig. 1). The articular facet for the head of the rib rises 

 gradually on the side of the centrum, the tubercular articulation remain- 

 ing on the diapophysis. None of the cervicals have a neural spine. 

 The neural canal is comparatively small. The centra of all the cervi- 

 cals have deep excavations in the sides, and the transverse processes 

 are more or less cavernous. The posterior cervicals which bear free 

 ribs are remarkable for the great size of the zygapophyses, which are 

 here much larger than elsewhere in the series. The anterior cervicals 

 have several lateral cavities, while those farther back have only one 

 large foramen in each side of the centrum, as in the dorsals. 



THE DORSAL VERTEBRA. 



The dorsal vertebra? of this species have short centra, more or less 

 opisthoccelian. There is a very large cavity in each side, which is sep- 

 arated from the one opposite by a thin vertical partition. The neural 

 canal is much larger than in the cervicals. The anterior dorsals are 

 distinctly opisthoccelian. The neural spine has no prominence in this 

 region, but rises rapidly farther back. In PI. XXI, figs. 2 and 3, a pos- 

 terior dorsal is represented, which shows the peculiar character of the 

 vertebra in this part of the series. The neural spine is greatly devel- 

 oped and has its summit transversely expanded. The vertebra? in this 

 region, as in all the known Sauropoda, have the peculiar diplosphenal 



